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    Rambda

    Faster alternative to Ramda in just 10kB
    Filed under  › 

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    Rambda

    Rambda is smaller and faster alternative to the popular functional programming library Ramda. - Documentation

    CircleCI codecov Commit activity All contributors Library size install size

    ❯ Example use

    import { compose, map, filter } from 'rambda'
    
    const result = compose(
      map(x => x * 2),
      filter(x => x > 2)
    )([1, 2, 3, 4])
    // => [6, 8]
    

    You can test this example in Rambda's REPL

    ---------------

    ❯ Rambda's advantages

    Typescript included

    Typescript definitions are included in the library, in comparison to Ramda, where you need to additionally install @types/ramda.

    Still, you need to be aware that functional programming features in Typescript are in development, which means that using R.compose/R.pipe can be problematic.

    Important - Rambda version 7.1.0(or higher) requires Typescript version 4.3.3(or higher).

    Immutable TS definitions

    You can use immutable version of Rambda definitions, which is linted with ESLint functional/prefer-readonly-type plugin.

    import {add} from 'rambda/immutable'
    

    Deno support

    While Ramda is available for Deno users, Rambda provides you with included TS definitions:

    import * as R from "https://x.nest.land/rambda@7.1.0/mod.ts";
    import * as Ramda from "https://x.nest.land/ramda@0.28.0/mod.ts";
    
    R.add(1)('foo') // => will trigger warning in VSCode
    Ramda.add(1)('foo') // => will not trigger warning in VSCode
    

    Smaller size

    The size of a library affects not only the build bundle size but also the dev bundle size and build time. This is important advantage, expecially for big projects.

    Tree-shaking

    Currently Rambda is more tree-shakable than Ramda - proven in the following repo.

    The repo holds two Angular9 applications: one with small example code of Ramda and the other - same code but with Rambda as import library.

    The test shows that Rambda bundle size is 2 MB less than its Ramda counterpart.

    There is also Webpack/Rollup/Parcel/Esbuild tree-shaking example including several libraries including Ramda, Rambda and Rambdax.

    actually tree-shaking is the initial reason for creation of Rambda

    Dot notation for R.path, R.paths, R.assocPath and R.lensPath

    Standard usage of R.path is R.path(['a', 'b'], {a: {b: 1} }).

    In Rambda you have the choice to use dot notation(which is arguably more readable):

    R.path('a.b', {a: {b: 1} })
    

    Comma notation for R.pick and R.omit

    Similar to dot notation, but the separator is comma(,) instead of dot(.).

    R.pick('a,b', {a: 1 , b: 2, c: 3} })
    // No space allowed between properties
    

    Speed

    Rambda is generally more performant than Ramda as the benchmarks can prove that.

    Deno

    Support

    As the library is smaller than Ramda, issues are much faster resolved.

    Closing the issue is usually accompanied by publishing a new patch version of Rambda to NPM.

    ---------------

    ❯ Missing Ramda methods

    Click to see the full list of 80 Ramda methods not implemented in Rambda - __ - addIndex - ap - aperture - applyTo - ascend - binary - call - collectBy - comparator - composeWith - construct - constructN - descend - differenceWith - dissocPath - empty - eqBy - forEachObjIndexed - gt - gte - hasIn - innerJoin - insert - insertAll - into - invert - invertObj - invoker - keysIn - lift - liftN - lt - lte - mapAccum - mapAccumRight - memoizeWith - mergeDeepLeft - mergeDeepWith - mergeDeepWithKey - mergeWithKey - modify - modifyPath - nAry - nthArg - o - otherwise - pair - partialRight - pathSatisfies - pickBy - pipeWith - project - promap - reduceBy - reduceRight - reduceWhile - reduced - remove - scan - sequence - sortWith - splitWhenever - symmetricDifferenceWith - andThen - toPairsIn - transduce - traverse - unary - uncurryN - unfold - unionWith - uniqBy - unnest - until - useWith - valuesIn - xprod - thunkify - default

    ---------------

    ❯ Install

    • yarn add rambda

    • For UMD usage either use ./dist/rambda.umd.js or the following CDN link:

    https://unpkg.com/rambda@CURRENT_VERSION/dist/rambda.umd.js
    
    • with deno
    import {compose, add} from 'https://raw.githubusercontent.com/selfrefactor/rambda/master/dist/rambda.esm.js'
    

    ---------------

    Differences between Rambda and Ramda

    • Rambda's type detects async functions and unresolved Promises. The returned values are 'Async' and 'Promise'.

    • Rambda's type handles NaN input, in which case it returns NaN.

    • Rambda's forEach can iterate over objects not only arrays.

    • Rambda's map, filter, partition when they iterate over objects, they pass property and input object as predicate's argument.

    • Rambda's filter returns empty array with bad input(null or undefined), while Ramda throws.

    • Ramda's clamp work with strings, while Rambda's method work only with numbers.

    • Ramda's indexOf/lastIndexOf work with strings and lists, while Rambda's method work only with lists as iterable input.

    • Error handling, when wrong inputs are provided, may not be the same. This difference will be better documented once all brute force tests are completed.

    • Typescript definitions between rambda and @types/ramda may vary.

    If you need more Ramda methods in Rambda, you may either submit a PR or check the extended version of Rambda - Rambdax. In case of the former, you may want to consult with Rambda contribution guidelines.

    ---------------

    ❯ Benchmarks

    Click to expand all benchmark results There are methods which are benchmarked only with Ramda and Rambda(i.e. no Lodash). Note that some of these methods, are called with and without curring. This is done in order to give more detailed performance feedback. The benchmarks results are produced from latest versions of Rambda, Lodash(4.17.21) and Ramda(0.28.0). method | Rambda | Ramda | Lodash --- |--- | --- | --- add | 🚀 Fastest | 21.52% slower | 82.15% slower adjust | 8.48% slower | 🚀 Fastest | 🔳 all | 🚀 Fastest | 3.79% slower | 🔳 allPass | 🚀 Fastest | 87.3% slower | 🔳 allPass | 🚀 Fastest | 98.56% slower | 🔳 and | 🚀 Fastest | 89.09% slower | 🔳 any | 🚀 Fastest | 92.87% slower | 45.82% slower anyPass | 🚀 Fastest | 98.25% slower | 🔳 append | 🚀 Fastest | 2.07% slower | 🔳 applySpec | 🚀 Fastest | 80.43% slower | 🔳 assoc | 72.32% slower | 60.08% slower | 🚀 Fastest clone | 🚀 Fastest | 91.86% slower | 86.48% slower compose | 1.91% slower | 21.6% slower | 🚀 Fastest converge | 78.63% slower | 🚀 Fastest | 🔳 curry | 🚀 Fastest | 28.86% slower | 🔳 curryN | 🚀 Fastest | 41.05% slower | 🔳 defaultTo | 🚀 Fastest | 48.91% slower | 🔳 drop | 🚀 Fastest | 82.35% slower | 🔳 dropLast | 🚀 Fastest | 86.74% slower | 🔳 equals | 58.37% slower | 96.73% slower | 🚀 Fastest filter | 6.7% slower | 72.03% slower | 🚀 Fastest find | 🚀 Fastest | 85.14% slower | 42.65% slower findIndex | 🚀 Fastest | 86.48% slower | 72.27% slower flatten | 🚀 Fastest | 95.26% slower | 10.27% slower ifElse | 🚀 Fastest | 58.56% slower | 🔳 includes | 🚀 Fastest | 84.68% slower | 🔳 indexOf | 🚀 Fastest | 83.07% slower | 🔳 indexOf | 🚀 Fastest | 82.2% slower | 🔳 init | 🚀 Fastest | 92.24% slower | 13.3% slower is | 🚀 Fastest | 57.69% slower | 🔳 isEmpty | 🚀 Fastest | 97.14% slower | 54.99% slower last | 🚀 Fastest | 93.43% slower | 5.28% slower lastIndexOf | 🚀 Fastest | 85.19% slower | 🔳 map | 🚀 Fastest | 86.6% slower | 11.73% slower match | 🚀 Fastest | 44.83% slower | 🔳 merge | 🚀 Fastest | 12.21% slower | 55.76% slower none | 🚀 Fastest | 96.48% slower | 🔳 objOf | 🚀 Fastest | 38.05% slower | 🔳 omit | 🚀 Fastest | 69.95% slower | 97.34% slower over | 🚀 Fastest | 56.23% slower | 🔳 path | 37.81% slower | 77.81% slower | 🚀 Fastest pick | 🚀 Fastest | 19.07% slower | 80.2% slower pipe | 0.41% slower | 🚀 Fastest | 🔳 prop | 🚀 Fastest | 87.95% slower | 🔳 propEq | 🚀 Fastest | 91.92% slower | 🔳 range | 🚀 Fastest | 61.8% slower | 57.44% slower reduce | 60.48% slower | 77.1% slower | 🚀 Fastest repeat | 48.57% slower | 68.98% slower | 🚀 Fastest replace | 33.45% slower | 33.99% slower | 🚀 Fastest set | 🚀 Fastest | 50.35% slower | 🔳 sort | 🚀 Fastest | 40.23% slower | 🔳 sortBy | 🚀 Fastest | 25.29% slower | 56.88% slower split | 🚀 Fastest | 55.37% slower | 17.64% slower splitEvery | 🚀 Fastest | 71.98% slower | 🔳 take | 🚀 Fastest | 91.96% slower | 4.72% slower takeLast | 🚀 Fastest | 93.39% slower | 19.22% slower test | 🚀 Fastest | 82.34% slower | 🔳 type | 🚀 Fastest | 48.6% slower | 🔳 uniq | 🚀 Fastest | 86.73% slower | 🔳 uniqWith | 13.67% slower | 🚀 Fastest | 🔳 uniqWith | 14.23% slower | 🚀 Fastest | 🔳 update | 🚀 Fastest | 52.35% slower | 🔳 view | 🚀 Fastest | 76.15% slower | 🔳

    ---------------

    ❯ Used by

    ---------------

    API

    add

    
    add(a: number, b: number): number
    

    It adds a and b.

    :boom: It doesn't work with strings, as the inputs are parsed to numbers before calculation.

    R.add(2, 3) // =>  5
    

    Try this R.add example in Rambda REPL

    All Typescript definitions typescript add(a: number, b: number): number; add(a: number): (b: number) => number;
    R.add source javascript export function add(a, b){ if (arguments.length === 1) return _b => add(a, _b) return Number(a) + Number(b) }
    Tests javascript import { add as addRamda } from 'ramda' import { compareCombinations } from './_internals/testUtils.js' import { add } from './add.js' test('with number', () => { expect(add(2, 3)).toEqual(5) expect(add(7)(10)).toEqual(17) }) test('string is bad input', () => { expect(add('foo', 'bar')).toBeNaN() }) test('ramda specs', () => { expect(add('1', '2')).toEqual(3) expect(add(1, '2')).toEqual(3) expect(add(true, false)).toEqual(1) expect(add(null, null)).toEqual(0) expect(add(undefined, undefined)).toEqual(NaN) expect(add(new Date(1), new Date(2))).toEqual(3) }) const possibleInputs = [ /foo/, 'foo', true, 3, NaN, 4, [], Promise.resolve(1), ] describe('brute force', () => { compareCombinations({ fn : add, fnRamda : addRamda, firstInput : possibleInputs, secondInput : possibleInputs, callback : errorsCounters => { expect(errorsCounters).toMatchInlineSnapshot(` Object { "ERRORS_MESSAGE_MISMATCH": 0, "ERRORS_TYPE_MISMATCH": 0, "RESULTS_MISMATCH": 0, "SHOULD_NOT_THROW": 0, "SHOULD_THROW": 0, "TOTAL_TESTS": 64, } `) }, }) })
    Typescript test typescript import {add} from 'rambda' describe('R.add', () => { it('happy', () => { const result = add(4, 1) result // $ExpectType number }) it('curried', () => { const result = add(4)(1) result // $ExpectType number }) })
    Rambda is fastest. Ramda is 21.52% slower and Lodash is 82.15% slower text const R = require('../../dist/rambda.js') const add = [ { label : 'Rambda', fn : () => { R.add(1, 1) }, }, { label : 'Ramda', fn : () => { Ramda.add(1, 1) }, }, { label : 'Lodash', fn : () => { _.add(1, 1) }, }, ]

    ---------------

    adjust

    
    adjust<T>(index: number, replaceFn: (x: T) => T, list: T[]): T[]
    

    It replaces index in array list with the result of replaceFn(list[i]).

    R.adjust(
      0,
      a => a + 1,
      [0, 100]
    ) // => [1, 100]
    

    Try this R.adjust example in Rambda REPL

    All Typescript definitions typescript adjust<T>(index: number, replaceFn: (x: T) => T, list: T[]): T[]; adjust<T>(index: number, replaceFn: (x: T) => T): (list: T[]) => T[];
    R.adjust source javascript import { cloneList } from './_internals/cloneList.js' import { curry } from './curry.js' function adjustFn( index, replaceFn, list ){ const actualIndex = index < 0 ? list.length + index : index if (index >= list.length || actualIndex < 0) return list const clone = cloneList(list) clone[ actualIndex ] = replaceFn(clone[ actualIndex ]) return clone } export const adjust = curry(adjustFn)
    Tests javascript import { add } from './add.js' import { adjust } from './adjust.js' import { pipe } from './pipe.js' const list = [ 0, 1, 2 ] const expected = [ 0, 11, 2 ] test('happy', () => {}) test('happy', () => { expect(adjust( 1, add(10), list )).toEqual(expected) }) test('with curring type 1 1 1', () => { expect(adjust(1)(add(10))(list)).toEqual(expected) }) test('with curring type 1 2', () => { expect(adjust(1)(add(10), list)).toEqual(expected) }) test('with curring type 2 1', () => { expect(adjust(1, add(10))(list)).toEqual(expected) }) test('with negative index', () => { expect(adjust( -2, add(10), list )).toEqual(expected) }) test('when index is out of bounds', () => { const list = [ 0, 1, 2, 3 ] expect(adjust( 4, add(1), list )).toEqual(list) expect(adjust( -5, add(1), list )).toEqual(list) })
    Rambda is slower than Ramda with 8.48% text const R = require('../../dist/rambda.js') const list = [ 0, 1, 2 ] const fn = x => x + 1 const index = 1 const adjust = [ { label : 'Rambda', fn : () => { R.adjust( index, fn, list ) R.adjust(index, fn)(list) }, }, { label : 'Ramda', fn : () => { Ramda.adjust( index, fn, list ) Ramda.adjust(index, fn)(list) }, }, ]

    ---------------

    all

    
    all<T>(predicate: (x: T) => boolean, list: T[]): boolean
    

    It returns true, if all members of array list returns true, when applied as argument to predicate function.

    const list = [ 0, 1, 2, 3, 4 ]
    const predicate = x => x > -1
    
    const result = R.all(predicate, list)
    // => true
    

    Try this R.all example in Rambda REPL

    All Typescript definitions typescript all<T>(predicate: (x: T) => boolean, list: T[]): boolean; all<T>(predicate: (x: T) => boolean): (list: T[]) => boolean;
    R.all source javascript export function all(predicate, list){ if (arguments.length === 1) return _list => all(predicate, _list) for (let i = 0; i < list.length; i++){ if (!predicate(list[ i ])) return false } return true }
    Tests javascript import { all } from './all.js' const list = [ 0, 1, 2, 3, 4 ] test('when true', () => { const fn = x => x > -1 expect(all(fn)(list)).toBeTrue() }) test('when false', () => { const fn = x => x > 2 expect(all(fn, list)).toBeFalse() })
    Typescript test typescript import {all} from 'rambda' describe('all', () => { it('happy', () => { const result = all( x => { x // $ExpectType number return x > 0 }, [1, 2, 3] ) result // $ExpectType boolean }) it('curried needs a type', () => { const result = all<number>(x => { x // $ExpectType number return x > 0 })([1, 2, 3]) result // $ExpectType boolean }) })
    Rambda is faster than Ramda with 3.79% text const R = require('../../dist/rambda.js') const { uniqListOfObjects, uniqListOfStrings, rangeOfNumbers, uniqListOfLists, } = require('./_utils.js') const limit = 100 const modes = [ [ uniqListOfObjects(limit), x => Object.keys(x).length > 2 ], [ uniqListOfStrings(limit), x => x.length > 0 ], [ uniqListOfLists(limit), x => x.length > 0 ], [ rangeOfNumbers(limit), x => x > -1 ], ] const applyBenchmark = (fn, input) => fn(input[ 1 ], input[ 0 ]) const tests = [ { label : 'Rambda', fn : R.all, }, { label : 'Ramda', fn : Ramda.all, }, ] tests, applyBenchmark, modes, }

    ---------------

    allPass

    
    allPass<T>(predicates: ((x: T) => boolean)[]): (input: T) => boolean
    

    It returns true, if all functions of predicates return true, when input is their argument.

    const input = {
      a : 1,
      b : 2,
    }
    const predicates = [
      x => x.a === 1,
      x => x.b === 2,
    ]
    const result = R.allPass(predicates)(input) // => true
    

    Try this R.allPass example in Rambda REPL

    All Typescript definitions typescript allPass<T>(predicates: ((x: T) => boolean)[]): (input: T) => boolean;
    R.allPass source javascript export function allPass(predicates){ return (...input) => { let counter = 0 while (counter < predicates.length){ if (!predicates[ counter ](...input)){ return false } counter++ } return true } }
    Tests javascript import { allPass } from './allPass.js' test('happy', () => { const rules = [ x => typeof x === 'number', x => x > 10, x => x * 7 < 100 ] expect(allPass(rules)(11)).toBeTrue() expect(allPass(rules)(undefined)).toBeFalse() }) test('when returns true', () => { const conditionArr = [ val => val.a === 1, val => val.b === 2 ] expect(allPass(conditionArr)({ a : 1, b : 2, })).toBeTrue() }) test('when returns false', () => { const conditionArr = [ val => val.a === 1, val => val.b === 3 ] expect(allPass(conditionArr)({ a : 1, b : 2, })).toBeFalse() }) test('works with multiple inputs', () => { const fn = function ( w, x, y, z ){ return w + x === y + z } expect(allPass([ fn ])( 3, 3, 3, 3 )).toBeTrue() })
    Typescript test typescript import {allPass} from 'rambda' describe('allPass', () => { it('happy', () => { const x = allPass<number>([ y => { y // $ExpectType number return typeof y === 'number' }, y => { return y > 0 }, ])(11) x // $ExpectType boolean }) })
    Rambda is faster than Ramda with 87.3% text const R = require('../../dist/rambda.js') const { random } = require('rambdax') const limit = 100 const min = 10 const max = 1200 function createListOfFunctions(fn, fnLimit){ return Array(fnLimit) .fill(null) .map(() => fn()) } const modes = [ [ { foo : 1500 }, createListOfFunctions(() => x => Number(x.foo) > random(min, max), limit), ], [ '1500', createListOfFunctions(() => x => Number(x) > random(min, max), limit), ], [ [ 1, 2, 1500 ], createListOfFunctions(() => x => x[ 2 ] > random(min, max), limit), ], [ 1500, createListOfFunctions(() => x => x > random(min, max), limit) ], ] const applyBenchmark = (fn, input) => fn(input[ 1 ])(input[ 0 ]) const tests = [ { label : 'Rambda', fn : R.allPass, }, { label : 'Ramda', fn : Ramda.allPass, }, ] tests, modes, applyBenchmark, }

    ---------------

    always

    
    always<T>(x: T): (...args: unknown[]) => T
    

    It returns function that always returns x.

    const fn = R.always(7)
    
    const result = fn()
    // => 7
    

    Try this R.always example in Rambda REPL

    All Typescript definitions typescript always<T>(x: T): (...args: unknown[]) => T;
    R.always source javascript export function always(x){ return _ => x }
    Tests javascript import { always } from './always.js' import { applySpec } from './applySpec.js' test('happy', () => { const fn = always(7) expect(fn()).toBe(7) expect(fn()).toBe(7) }) test('compatibility with applySpec', () => { const spec = applySpec({ x : always('foo') }) expect(spec({})).toEqual({ x : 'foo' }) })
    Typescript test typescript import {always} from 'rambda' describe('R.always', () => { it('happy', () => { const fn = always('foo') fn // $ExpectType (...args: unknown[]) => string const result = fn() result // $ExpectType string }) })

    ---------------

    and

    Logical AND

    R.and(true, true); // => true
    R.and(false, true); // => false
    R.and(true, 'foo'); // => 'foo'
    

    Try this R.and example in Rambda REPL

    ---------------

    any

    
    any<T>(predicate: (x: T) => boolean, list: T[]): boolean
    

    It returns true, if at least one member of list returns true, when passed to a predicate function.

    const list = [1, 2, 3]
    const predicate = x => x * x > 8
    R.any(fn, list)
    // => true
    

    Try this R.any example in Rambda REPL

    All Typescript definitions typescript any<T>(predicate: (x: T) => boolean, list: T[]): boolean; any<T>(predicate: (x: T) => boolean): (list: T[]) => boolean;
    R.any source javascript export function any(predicate, list){ if (arguments.length === 1) return _list => any(predicate, _list) let counter = 0 while (counter < list.length){ if (predicate(list[ counter ], counter)){ return true } counter++ } return false }
    Tests javascript import { any } from './any.js' const list = [ 1, 2, 3 ] test('happy', () => { expect(any(x => x < 0, list)).toBeFalse() }) test('with curry', () => { expect(any(x => x > 2)(list)).toBeTrue() })
    Typescript test typescript import {any} from 'rambda' describe('R.any', () => { it('happy', () => { const result = any( x => { x // $ExpectType number return x > 2 }, [1, 2, 3] ) result // $ExpectType boolean }) it('when curried needs a type', () => { const result = any<number>(x => { x // $ExpectType number return x > 2 })([1, 2, 3]) result // $ExpectType boolean }) })
    Rambda is fastest. Ramda is 92.87% slower and Lodash is 45.82% slower text const R = require('../../dist/rambda.js') const input = [ 1, 2, 3, 4 ] const fn = val => val > 2 const any = [ { label : 'Rambda', fn : () => { R.any(fn, input) }, }, { label : 'Ramda', fn : () => { Ramda.any(fn, input) }, }, { label : 'Lodash.some', fn : () => { _.some(input, fn) }, }, ]

    ---------------

    anyPass

    
    anyPass<T>(predicates: SafePred<T>[]): SafePred<T>
    

    It accepts list of predicates and returns a function. This function with its input will return true, if any of predicates returns true for this input.

    const isBig = x => x > 20
    const isOdd = x => x % 2 === 1
    const input = 11
    
    const fn = R.anyPass(
      [isBig, isOdd]
    )
    
    const result = fn(input) 
    // => true
    

    Try this R.anyPass example in Rambda REPL

    All Typescript definitions typescript anyPass<T>(predicates: SafePred<T>[]): SafePred<T>;
    R.anyPass source javascript export function anyPass(predicates){ return (...input) => { let counter = 0 while (counter < predicates.length){ if (predicates[ counter ](...input)){ return true } counter++ } return false } }
    Tests javascript import {anyPass} from './anyPass.js' test('happy', () => { const rules = [x => typeof x === 'string', x => x > 10] const predicate = anyPass(rules) expect(predicate('foo')).toBeTrue() expect(predicate(6)).toBeFalse() }) test('happy', () => { const rules = [x => typeof x === 'string', x => x > 10] expect(anyPass(rules)(11)).toBeTrue() expect(anyPass(rules)(undefined)).toBeFalse() }) const obj = { a: 1, b: 2, } test('when returns true', () => { const conditionArr = [val => val.a === 1, val => val.a === 2] expect(anyPass(conditionArr)(obj)).toBeTrue() }) test('when returns false + curry', () => { const conditionArr = [val => val.a === 2, val => val.b === 3] expect(anyPass(conditionArr)(obj)).toBeFalse() }) test('with empty predicates list', () => { expect(anyPass([])(3)).toBeFalse() }) test('works with multiple inputs', () => { const fn = function (w, x, y, z) { console.log(w, x, y, z) return w + x === y + z } expect(anyPass([fn])(3, 3, 3, 3)).toBeTrue() })
    Typescript test typescript import {anyPass} from 'rambda' describe('anyPass', () => { it('happy', () => { const x = anyPass<number>([ y => { y // $ExpectType number return typeof y === 'number' }, y => { return y > 0 }, ])(11) x // $ExpectType boolean }) })
    Rambda is faster than Ramda with 98.25% text const R = require('../../dist/rambda.js') const rules = [ x => typeof x === 'boolean', x => x > 20, x => x * 7 < 100 ] const anyPass = [ { label : 'Rambda', fn : () => { R.anyPass(rules)(11) }, }, { label : 'Ramda', fn : () => { Ramda.anyPass(rules)(11) }, }, ]

    ---------------

    append

    
    append<T>(x: T, list: T[]): T[]
    

    It adds element x at the end of list.

    const x = 'foo'
    
    const result = R.append(x, ['bar', 'baz'])
    // => ['bar', 'baz', 'foo']
    

    Try this R.append example in Rambda REPL

    All Typescript definitions typescript append<T>(x: T, list: T[]): T[]; append<T>(x: T): <T>(list: T[]) => T[];
    R.append source javascript import { cloneList } from './_internals/cloneList.js' export function append(x, input){ if (arguments.length === 1) return _input => append(x, _input) if (typeof input === 'string') return input.split('').concat(x) const clone = cloneList(input) clone.push(x) return clone }
    Tests javascript import { append } from './append.js' test('happy', () => { expect(append('tests', [ 'write', 'more' ])).toEqual([ 'write', 'more', 'tests', ]) }) test('append to empty array', () => { expect(append('tests')([])).toEqual([ 'tests' ]) }) test('with strings', () => { expect(append('o', 'fo')).toEqual([ 'f', 'o', 'o' ]) })
    Typescript test typescript import {append} from 'rambda' const list = [1, 2, 3] describe('R.append', () => { it('happy', () => { const result = append(4, list) result // $ExpectType number[] }) it('curried', () => { const result = append(4)(list) result // $ExpectType number[] }) })
    Rambda is faster than Ramda with 2.07% text const R = require('../../dist/rambda.js') const append = [ { label : 'Rambda', fn : () => { R.append(0)([ 1, 2, 3, 4 ]) R.append('bar')('foo') }, }, { label : 'Ramda', fn : () => { Ramda.append(0)([ 1, 2, 3, 4 ]) Ramda.append('bar')('foo') }, }, ]

    ---------------

    apply

    
    apply<T = any>(fn: (...args: any[]) => T, args: any[]): T
    

    It applies function fn to the list of arguments.

    This is useful for creating a fixed-arity function from a variadic function. fn should be a bound function if context is significant.

    const result = R.apply(Math.max, [42, -Infinity, 1337])
    // => 1337
    

    Try this R.apply example in Rambda REPL

    All Typescript definitions typescript apply<T = any>(fn: (...args: any[]) => T, args: any[]): T; apply<T = any>(fn: (...args: any[]) => T): (args: any[]) => T;
    R.apply source javascript export function apply(fn, args){ if (arguments.length === 1){ return _args => apply(fn, _args) } return fn.apply(this, args) }
    Tests javascript import {apply} from './apply.js' import {bind} from './bind.js' import {identity} from './identity.js' test('happy', () => { expect(apply(identity, [1, 2, 3])).toEqual(1) }) test('applies function to argument list', () => { expect(apply(Math.max, [1, 2, 3, -99, 42, 6, 7])).toEqual(42) }) test('provides no way to specify context', () => { const obj = { method: function () { return this === obj }, } expect(apply(obj.method, [])).toBeFalse() expect(apply(bind(obj.method, obj), [])).toBeTrue() })
    Typescript test typescript import {apply, identity} from 'rambda' describe('R.apply', () => { it('happy', () => { const result = apply<number>(identity, [1, 2, 3]) result // $ExpectType number }) it('curried', () => { const fn = apply<number>(identity) const result = fn([1, 2, 3]) result // $ExpectType number }) })

    ---------------

    applySpec

    
    applySpec<Spec extends Record<string, (...args: any[]) => any>>(
      spec: Spec
    ): (
      ...args: Parameters<ValueOfRecord<Spec>>
    ) => { [Key in keyof Spec]: ReturnType<Spec[Key]> }
    

    :boom: The currying in this function works best with functions with 4 arguments or less. (arity of 4)

    const fn = R.applySpec({
      sum: R.add,
      nested: { mul: R.multiply }
    })
    const result = fn(2, 4) 
    // => { sum: 6, nested: { mul: 8 } }
    

    Try this R.applySpec example in Rambda REPL

    All Typescript definitions typescript applySpec<Spec extends Record<string, (...args: any[]) => any>>( spec: Spec ): ( ...args: Parameters<ValueOfRecord<Spec>> ) => { [Key in keyof Spec]: ReturnType<Spec[Key]> }; applySpec<T>(spec: any): (...args: any[]) => T;
    R.applySpec source javascript import { _isArray } from './_internals/_isArray.js' // recursively traverse the given spec object to find the highest arity function export function __findHighestArity(spec, max = 0){ for (const key in spec){ if (spec.hasOwnProperty(key) === false || key === 'constructor') continue if (typeof spec[ key ] === 'object'){ max = Math.max(max, __findHighestArity(spec[ key ])) } if (typeof spec[ key ] === 'function'){ max = Math.max(max, spec[ key ].length) } } return max } function __filterUndefined(){ const defined = [] let i = 0 const l = arguments.length while (i < l){ if (typeof arguments[ i ] === 'undefined') break defined[ i ] = arguments[ i ] i++ } return defined } function __applySpecWithArity( spec, arity, cache ){ const remaining = arity - cache.length if (remaining === 1) return x => __applySpecWithArity( spec, arity, __filterUndefined(...cache, x) ) if (remaining === 2) return (x, y) => __applySpecWithArity( spec, arity, __filterUndefined( ...cache, x, y ) ) if (remaining === 3) return ( x, y, z ) => __applySpecWithArity( spec, arity, __filterUndefined( ...cache, x, y, z ) ) if (remaining === 4) return ( x, y, z, a ) => __applySpecWithArity( spec, arity, __filterUndefined( ...cache, x, y, z, a ) ) if (remaining > 4) return (...args) => __applySpecWithArity( spec, arity, __filterUndefined(...cache, ...args) ) // handle spec as Array if (_isArray(spec)){ const ret = [] let i = 0 const l = spec.length for (; i < l; i++){ // handle recursive spec inside array if (typeof spec[ i ] === 'object' || _isArray(spec[ i ])){ ret[ i ] = __applySpecWithArity( spec[ i ], arity, cache ) } // apply spec to the key if (typeof spec[ i ] === 'function'){ ret[ i ] = spec[ i ](...cache) } } return ret } // handle spec as Object const ret = {} // apply callbacks to each property in the spec object for (const key in spec){ if (spec.hasOwnProperty(key) === false || key === 'constructor') continue // apply the spec recursively if (typeof spec[ key ] === 'object'){ ret[ key ] = __applySpecWithArity( spec[ key ], arity, cache ) continue } // apply spec to the key if (typeof spec[ key ] === 'function'){ ret[ key ] = spec[ key ](...cache) } } return ret } export function applySpec(spec, ...args){ // get the highest arity spec function, cache the result and pass to __applySpecWithArity const arity = __findHighestArity(spec) if (arity === 0){ return () => ({}) } const toReturn = __applySpecWithArity( spec, arity, args ) return toReturn }
    Tests javascript import { applySpec as applySpecRamda, nAry } from 'ramda' import { add, always, compose, dec, inc, map, path, prop, T } from '../rambda.js' import { applySpec } from './applySpec.js' test('different than Ramda when bad spec', () => { const result = applySpec({ sum : { a : 1 } })(1, 2) const ramdaResult = applySpecRamda({ sum : { a : 1 } })(1, 2) expect(result).toEqual({}) expect(ramdaResult).toEqual({ sum : { a : {} } }) }) test('works with empty spec', () => { expect(applySpec({})()).toEqual({}) expect(applySpec([])(1, 2)).toEqual({}) expect(applySpec(null)(1, 2)).toEqual({}) }) test('works with unary functions', () => { const result = applySpec({ v : inc, u : dec, })(1) const expected = { v : 2, u : 0, } expect(result).toEqual(expected) }) test('works with binary functions', () => { const result = applySpec({ sum : add })(1, 2) expect(result).toEqual({ sum : 3 }) }) test('works with nested specs', () => { const result = applySpec({ unnested : always(0), nested : { sum : add }, })(1, 2) const expected = { unnested : 0, nested : { sum : 3 }, } expect(result).toEqual(expected) }) test('works with arrays of nested specs', () => { const result = applySpec({ unnested : always(0), nested : [ { sum : add } ], })(1, 2) expect(result).toEqual({ unnested : 0, nested : [ { sum : 3 } ], }) }) test('works with arrays of spec objects', () => { const result = applySpec([ { sum : add } ])(1, 2) expect(result).toEqual([ { sum : 3 } ]) }) test('works with arrays of functions', () => { const result = applySpec([ map(prop('a')), map(prop('b')) ])([ { a : 'a1', b : 'b1', }, { a : 'a2', b : 'b2', }, ]) const expected = [ [ 'a1', 'a2' ], [ 'b1', 'b2' ], ] expect(result).toEqual(expected) }) test('works with a spec defining a map key', () => { expect(applySpec({ map : prop('a') })({ a : 1 })).toEqual({ map : 1 }) }) test('cannot retains the highest arity', () => { const f = applySpec({ f1 : nAry(2, T), f2 : nAry(5, T), }) const fRamda = applySpecRamda({ f1 : nAry(2, T), f2 : nAry(5, T), }) expect(f.length).toBe(0) expect(fRamda.length).toBe(5) }) test('returns a curried function', () => { expect(applySpec({ sum : add })(1)(2)).toEqual({ sum : 3 }) }) // Additional tests // ============================================ test('arity', () => { const spec = { one : x1 => x1, two : (x1, x2) => x1 + x2, three : ( x1, x2, x3 ) => x1 + x2 + x3, } expect(applySpec( spec, 1, 2, 3 )).toEqual({ one : 1, two : 3, three : 6, }) }) test('arity over 5 arguments', () => { const spec = { one : x1 => x1, two : (x1, x2) => x1 + x2, three : ( x1, x2, x3 ) => x1 + x2 + x3, four : ( x1, x2, x3, x4 ) => x1 + x2 + x3 + x4, five : ( x1, x2, x3, x4, x5 ) => x1 + x2 + x3 + x4 + x5, } expect(applySpec( spec, 1, 2, 3, 4, 5 )).toEqual({ one : 1, two : 3, three : 6, four : 10, five : 15, }) }) test('curried', () => { const spec = { one : x1 => x1, two : (x1, x2) => x1 + x2, three : ( x1, x2, x3 ) => x1 + x2 + x3, } expect(applySpec(spec)(1)(2)(3)).toEqual({ one : 1, two : 3, three : 6, }) }) test('curried over 5 arguments', () => { const spec = { one : x1 => x1, two : (x1, x2) => x1 + x2, three : ( x1, x2, x3 ) => x1 + x2 + x3, four : ( x1, x2, x3, x4 ) => x1 + x2 + x3 + x4, five : ( x1, x2, x3, x4, x5 ) => x1 + x2 + x3 + x4 + x5, } expect(applySpec(spec)(1)(2)(3)(4)(5)).toEqual({ one : 1, two : 3, three : 6, four : 10, five : 15, }) }) test('undefined property', () => { const spec = { prop : path([ 'property', 'doesnt', 'exist' ]) } expect(applySpec(spec, {})).toEqual({ prop : undefined }) }) test('restructure json object', () => { const spec = { id : path('user.id'), name : path('user.firstname'), profile : path('user.profile'), doesntExist : path('user.profile.doesntExist'), info : { views : compose(inc, prop('views')) }, type : always('playa'), } const data = { user : { id : 1337, firstname : 'john', lastname : 'shaft', profile : 'shaft69', }, views : 42, } expect(applySpec(spec, data)).toEqual({ id : 1337, name : 'john', profile : 'shaft69', doesntExist : undefined, info : { views : 43 }, type : 'playa', }) })
    Typescript test typescript import {multiply, applySpec, inc, dec, add} from 'rambda' describe('applySpec', () => { it('ramda 1', () => { const result = applySpec({ v: inc, u: dec, })(1) result // $ExpectType { v: number; u: number; } }) it('ramda 1', () => { interface Output { sum: number multiplied: number } const result = applySpec<Output>({ sum: add, multiplied: multiply, })(1, 2) result // $ExpectType Output }) })
    Rambda is faster than Ramda with 80.43% text const R = require('../../dist/rambda.js') const curryN = [ { label : 'Rambda', fn : () => { const data = { a : { b : { c : 1 }, d : 2, }, } const spec = { c : R.path([ 'a', 'b', 'c' ]), d : R.path([ 'a', 'd' ]), } R.applySpec(spec, data) }, }, { label : 'Ramda', fn : () => { const data = { a : { b : { c : 1 }, d : 2, }, } const spec = { c : Ramda.path([ 'a', 'b', 'c' ]), d : Ramda.path([ 'a', 'd' ]), } Ramda.applySpec(spec, data) }, }, ]

    ---------------

    assoc

    
    assoc<T, U, K extends string>(prop: K, val: T, obj: U): Record<K, T> & Omit<U, K>
    

    It makes a shallow clone of obj with setting or overriding the property prop with newValue.

    :boom: This copies and flattens prototype properties onto the new object as well. All non-primitive properties are copied by reference.

    R.assoc('c', 3, {a: 1, b: 2})
    // => {a: 1, b: 2, c: 3}
    

    Try this R.assoc example in Rambda REPL

    All Typescript definitions typescript assoc<T, U, K extends string>(prop: K, val: T, obj: U): Record<K, T> & Omit<U, K>; assoc<T, K extends string>(prop: K, val: T): <U>(obj: U) => Record<K, T> & Omit<U, K>; assoc<K extends string>(prop: K): AssocPartialOne<K>;
    R.assoc source javascript import { curry } from './curry.js' function assocFn( prop, newValue, obj ){ return Object.assign( {}, obj, { [ prop ] : newValue } ) } export const assoc = curry(assocFn)
    Tests javascript import { assoc } from './assoc.js' test('adds a key to an empty object', () => { expect(assoc( 'a', 1, {} )).toEqual({ a : 1 }) }) test('adds a key to a non-empty object', () => { expect(assoc( 'b', 2, { a : 1 } )).toEqual({ a : 1, b : 2, }) }) test('adds a key to a non-empty object - curry case 1', () => { expect(assoc('b', 2)({ a : 1 })).toEqual({ a : 1, b : 2, }) }) test('adds a key to a non-empty object - curry case 2', () => { expect(assoc('b')(2, { a : 1 })).toEqual({ a : 1, b : 2, }) }) test('adds a key to a non-empty object - curry case 3', () => { const result = assoc('b')(2)({ a : 1 }) expect(result).toEqual({ a : 1, b : 2, }) }) test('changes an existing key', () => { expect(assoc( 'a', 2, { a : 1 } )).toEqual({ a : 2 }) }) test('undefined is considered an empty object', () => { expect(assoc( 'a', 1, undefined )).toEqual({ a : 1 }) }) test('null is considered an empty object', () => { expect(assoc( 'a', 1, null )).toEqual({ a : 1 }) }) test('value can be null', () => { expect(assoc( 'a', null, null )).toEqual({ a : null }) }) test('value can be undefined', () => { expect(assoc( 'a', undefined, null )).toEqual({ a : undefined }) }) test('assignment is shallow', () => { expect(assoc( 'a', { b : 2 }, { a : { c : 3 } } )).toEqual({ a : { b : 2 } }) })
    Typescript test typescript import {assoc} from 'rambda' const obj = {a: 1} const newValue = 2 const newProp = 'b' describe('R.assoc', () => { it('happy', () => { const result = assoc(newProp, newValue, obj) result.a // $ExpectType number result.b // $ExpectType number }) it('curried 1', () => { const result = assoc(newProp, newValue)(obj) result.a // $ExpectType number result.b // $ExpectType number }) it('curried 2', () => { const result = assoc(newProp)(newValue)(obj) result.a // $ExpectType number result.b // $ExpectType number }) })
    Lodash is fastest. Rambda is 72.32% slower and Ramda is 60.08% slower text const R = require('../../dist/rambda.js') const input = { a : 1, b : 2, } const key = 'c' const value = 3 const assoc = [ { label : 'Rambda', fn : () => { R.assoc( key, value, input ) }, }, { label : 'Ramda', fn : () => { Ramda.assoc( key, value, input ) }, }, { label : 'Lodash.set', fn : () => { _.set( input, key, value ) }, }, ]

    ---------------

    assocPath

    
    assocPath<Output>(path: Path, newValue: any, obj: object): Output
    

    It makes a shallow clone of obj with setting or overriding with newValue the property found with path.

    const path = 'b.c'
    const newValue = 2
    const obj = { a: 1 }
    
    R.assocPath(path, newValue, Record<string, unknown>)
    // => { a : 1, b : { c : 2 }}
    

    Try this R.assocPath example in Rambda REPL

    All Typescript definitions typescript assocPath<Output>(path: Path, newValue: any, obj: object): Output; assocPath<Output>(path: Path, newValue: any): (obj: object) => Output; assocPath<Output>(path: Path): (newValue: any) => (obj: object) => Output;
    R.assocPath source javascript import { _isArray } from './_internals/_isArray.js' import { _isInteger } from './_internals/_isInteger.js' import { cloneList } from './_internals/cloneList.js' import { assoc } from './assoc.js' import { curry } from './curry.js' function assocPathFn( path, newValue, input ){ const pathArrValue = typeof path === 'string' ? path.split('.').map(x => _isInteger(Number(x)) ? Number(x) : x) : path if (pathArrValue.length === 0){ return newValue } const index = pathArrValue[ 0 ] if (pathArrValue.length > 1){ const condition = typeof input !== 'object' || input === null || !input.hasOwnProperty(index) const nextinput = condition ? _isInteger(pathArrValue[ 1 ]) ? [] : {} : input[ index ] newValue = assocPathFn( Array.prototype.slice.call(pathArrValue, 1), newValue, nextinput ) } if (_isInteger(index) && _isArray(input)){ const arr = cloneList(input) arr[ index ] = newValue return arr } return assoc( index, newValue, input ) } export const assocPath = curry(assocPathFn)
    Tests javascript import { assocPath } from './assocPath.js' test('string can be used as path input', () => { const testObj = { a : [ { b : 1 }, { b : 2 } ], d : 3, } const result = assocPath( 'a.0.b', 10, testObj ) const expected = { a : [ { b : 10 }, { b : 2 } ], d : 3, } expect(result).toEqual(expected) }) test('bug', () => { /* https://github.com/selfrefactor/rambda/issues/524 */ const state = {} const withDateLike = assocPath( [ 'outerProp', '2020-03-10' ], { prop : 2 }, state ) const withNumber = assocPath( [ 'outerProp', '5' ], { prop : 2 }, state ) const withDateLikeExpected = { outerProp : { '2020-03-10' : { prop : 2 } } } const withNumberExpected = { outerProp : { 5 : { prop : 2 } } } expect(withDateLike).toEqual(withDateLikeExpected) expect(withNumber).toEqual(withNumberExpected) }) test('adds a key to an empty object', () => { expect(assocPath( [ 'a' ], 1, {} )).toEqual({ a : 1 }) }) test('adds a key to a non-empty object', () => { expect(assocPath( 'b', 2, { a : 1 } )).toEqual({ a : 1, b : 2, }) }) test('adds a nested key to a non-empty object', () => { expect(assocPath( 'b.c', 2, { a : 1 } )).toEqual({ a : 1, b : { c : 2 }, }) }) test('adds a nested key to a nested non-empty object - curry case 1', () => { expect(assocPath('b.d', 3)({ a : 1, b : { c : 2 }, })).toEqual({ a : 1, b : { c : 2, d : 3, }, }) }) test('adds a key to a non-empty object - curry case 1', () => { expect(assocPath('b', 2)({ a : 1 })).toEqual({ a : 1, b : 2, }) }) test('adds a nested key to a non-empty object - curry case 1', () => { expect(assocPath('b.c', 2)({ a : 1 })).toEqual({ a : 1, b : { c : 2 }, }) }) test('adds a key to a non-empty object - curry case 2', () => { expect(assocPath('b')(2, { a : 1 })).toEqual({ a : 1, b : 2, }) }) test('adds a key to a non-empty object - curry case 3', () => { const result = assocPath('b')(2)({ a : 1 }) expect(result).toEqual({ a : 1, b : 2, }) }) test('changes an existing key', () => { expect(assocPath( 'a', 2, { a : 1 } )).toEqual({ a : 2 }) }) test('undefined is considered an empty object', () => { expect(assocPath( 'a', 1, undefined )).toEqual({ a : 1 }) }) test('null is considered an empty object', () => { expect(assocPath( 'a', 1, null )).toEqual({ a : 1 }) }) test('value can be null', () => { expect(assocPath( 'a', null, null )).toEqual({ a : null }) }) test('value can be undefined', () => { expect(assocPath( 'a', undefined, null )).toEqual({ a : undefined }) }) test('assignment is shallow', () => { expect(assocPath( 'a', { b : 2 }, { a : { c : 3 } } )).toEqual({ a : { b : 2 } }) }) test('empty array as path', () => { const result = assocPath( [], 3, { a : 1, b : 2, } ) expect(result).toEqual(3) }) test('happy', () => { const expected = { foo : { bar : { baz : 42 } } } const result = assocPath( [ 'foo', 'bar', 'baz' ], 42, { foo : null } ) expect(result).toEqual(expected) })
    Typescript test typescript import {assocPath} from 'rambda' interface Output { a: number foo: {bar: number} } describe('R.assocPath - user must explicitly set type of output', () => { it('with array as path input', () => { const result = assocPath<Output>(['foo', 'bar'], 2, {a: 1}) result // $ExpectType Output }) it('with string as path input', () => { const result = assocPath<Output>('foo.bar', 2, {a: 1}) result // $ExpectType Output }) }) describe('R.assocPath - curried', () => { it('with array as path input', () => { const result = assocPath<Output>(['foo', 'bar'], 2)({a: 1}) result // $ExpectType Output }) it('with string as path input', () => { const result = assocPath<Output>('foo.bar', 2)({a: 1}) result // $ExpectType Output }) })

    ---------------

    bind

    
    bind<F extends (...args: any[]) => any, T>(fn: F, thisObj: T): (...args: Parameters<F>) => ReturnType<F>
    

    Creates a function that is bound to a context.

    :boom: R.bind does not provide the additional argument-binding capabilities of Function.prototype.bind.

    const log = R.bind(console.log, console)
    const result = R.pipe(
      R.assoc('a', 2), 
      R.tap(log), 
      R.assoc('a', 3)
    )({a: 1}); 
    // => result - `{a: 3}`
    // => console log - `{a: 2}`
    

    Try this R.bind example in Rambda REPL

    All Typescript definitions typescript bind<F extends (...args: any[]) => any, T>(fn: F, thisObj: T): (...args: Parameters<F>) => ReturnType<F>; bind<F extends (...args: any[]) => any, T>(fn: F): (thisObj: T) => (...args: Parameters<F>) => ReturnType<F>;
    R.bind source javascript import { curryN } from './curryN.js' export function bind(fn, thisObj){ if (arguments.length === 1){ return _thisObj => bind(fn, _thisObj) } return curryN(fn.length, (...args) => fn.apply(thisObj, args)) }
    Tests javascript import {bind} from './bind.js' function Foo(x) { this.x = x } function add(x) { return this.x + x } function Bar(x, y) { this.x = x this.y = y } Bar.prototype = new Foo() Bar.prototype.getX = function () { return 'prototype getX' } test('returns a function', () => { expect(typeof bind(add)(Foo)).toEqual('function') }) test('returns a function bound to the specified context object', () => { const f = new Foo(12) function isFoo() { return this instanceof Foo } const isFooBound = bind(isFoo, f) expect(isFoo()).toBeFalse() expect(isFooBound()).toBeTrue() }) test('works with built-in types', () => { const abc = bind(String.prototype.toLowerCase, 'ABCDEFG') expect(typeof abc).toEqual('function') expect(abc()).toEqual('abcdefg') }) test('works with user-defined types', () => { const f = new Foo(12) function getX() { return this.x } const getXFooBound = bind(getX, f) expect(getXFooBound()).toEqual(12) }) test('works with plain objects', () => { const pojso = {x: 100} function incThis() { return this.x + 1 } const incPojso = bind(incThis, pojso) expect(typeof incPojso).toEqual('function') expect(incPojso()).toEqual(101) }) test('does not interfere with existing object methods', () => { const b = new Bar('a', 'b') function getX() { return this.x } const getXBarBound = bind(getX, b) expect(b.getX()).toEqual('prototype getX') expect(getXBarBound()).toEqual('a') }) test('preserves arity', () => { const f0 = function () { return 0 } const f1 = function (a) { return a } const f2 = function (a, b) { return a + b } const f3 = function (a, b, c) { return a + b + c } expect(bind(f0, {}).length).toEqual(0) expect(bind(f1, {}).length).toEqual(1) expect(bind(f2, {}).length).toEqual(2) expect(bind(f3, {}).length).toEqual(3) })
    Typescript test typescript import {bind} from 'rambda' class Foo {} function isFoo<T = any>(this: T): boolean { return this instanceof Foo } describe('R.bind', () => { it('happy', () => { const foo = new Foo() const result = bind(isFoo, foo)() result // $ExpectType boolean }) })

    ---------------

    both

    
    both(pred1: Pred, pred2: Pred): Pred
    

    It returns a function with input argument.

    This function will return true, if both firstCondition and secondCondition return true when input is passed as their argument.

    const firstCondition = x => x > 10
    const secondCondition = x => x < 20
    const fn = R.both(firstCondition, secondCondition)
    
    const result = [fn(15), fn(30)]
    // => [true, false]
    

    Try this R.both example in Rambda REPL

    All Typescript definitions typescript both(pred1: Pred, pred2: Pred): Pred; both<T>(pred1: Predicate<T>, pred2: Predicate<T>): Predicate<T>; both<T>(pred1: Predicate<T>): (pred2: Predicate<T>) => Predicate<T>; both(pred1: Pred): (pred2: Pred) => Pred;
    R.both source javascript export function both(f, g){ if (arguments.length === 1) return _g => both(f, _g) return (...input) => f(...input) && g(...input) }
    Tests javascript import { both } from './both.js' const firstFn = val => val > 0 const secondFn = val => val < 10 test('with curry', () => { expect(both(firstFn)(secondFn)(17)).toBeFalse() }) test('without curry', () => { expect(both(firstFn, secondFn)(7)).toBeTrue() }) test('with multiple inputs', () => { const between = function ( a, b, c ){ return a < b && b < c } const total20 = function ( a, b, c ){ return a + b + c === 20 } const fn = both(between, total20) expect(fn( 5, 7, 8 )).toBeTrue() }) test('skip evaluation of the second expression', () => { let effect = 'not evaluated' const F = function (){ return false } const Z = function (){ effect = 'Z got evaluated' } both(F, Z)() expect(effect).toBe('not evaluated') })
    Typescript test typescript import {both} from 'rambda' describe('R.both', () => { it('with passed type', () => { const fn = both<number>( x => x > 1, x => x % 2 === 0 ) fn // $ExpectType Predicate<number> const result = fn(2) // $ExpectType boolean result // $ExpectType boolean }) it('with passed type - curried', () => { const fn = both<number>(x => x > 1)(x => x % 2 === 0) fn // $ExpectType Predicate<number> const result = fn(2) result // $ExpectType boolean }) it('no type passed', () => { const fn = both( x => { x // $ExpectType any return x > 1 }, x => { x // $ExpectType any return x % 2 === 0 } ) const result = fn(2) result // $ExpectType boolean }) it('no type passed - curried', () => { const fn = both((x: number) => { x // $ExpectType number return x > 1 })((x: number) => { x // $ExpectType number return x % 2 === 0 }) const result = fn(2) result // $ExpectType boolean }) })

    ---------------

    chain

    
    chain<T, U>(fn: (n: T) => U[], list: T[]): U[]
    

    The method is also known as flatMap.

    const duplicate = n => [ n, n ]
    const list = [ 1, 2, 3 ]
    
    const result = chain(duplicate, list)
    // => [ 1, 1, 2, 2, 3, 3 ]
    

    Try this R.chain example in Rambda REPL

    All Typescript definitions typescript chain<T, U>(fn: (n: T) => U[], list: T[]): U[]; chain<T, U>(fn: (n: T) => U[]): (list: T[]) => U[];
    R.chain source javascript export function chain(fn, list){ if (arguments.length === 1){ return _list => chain(fn, _list) } return [].concat(...list.map(fn)) }
    Tests javascript import { chain as chainRamda } from 'ramda' import { chain } from './chain.js' const duplicate = n => [ n, n ] test('happy', () => { const fn = x => [ x * 2 ] const list = [ 1, 2, 3 ] const result = chain(fn, list) expect(result).toEqual([ 2, 4, 6 ]) }) test('maps then flattens one level', () => { expect(chain(duplicate, [ 1, 2, 3 ])).toEqual([ 1, 1, 2, 2, 3, 3 ]) }) test('maps then flattens one level - curry', () => { expect(chain(duplicate)([ 1, 2, 3 ])).toEqual([ 1, 1, 2, 2, 3, 3 ]) }) test('flattens only one level', () => { const nest = n => [ [ n ] ] expect(chain(nest, [ 1, 2, 3 ])).toEqual([ [ 1 ], [ 2 ], [ 3 ] ]) }) test('can compose', () => { function dec(x){ return [ x - 1 ] } function times2(x){ return [ x * 2 ] } const mdouble = chain(times2) const mdec = chain(dec) expect(mdec(mdouble([ 10, 20, 30 ]))).toEqual([ 19, 39, 59 ]) }) test('@types/ramda broken test', () => { const score = { maths : 90, physics : 80, } const calculateTotal = score => { const { maths, physics } = score return maths + physics } const assocTotalToScore = (total, score) => ({ ...score, total, }) const calculateAndAssocTotalToScore = chainRamda(assocTotalToScore, calculateTotal) expect(() => calculateAndAssocTotalToScore(score)).toThrow() })
    Typescript test typescript import {chain} from 'rambda' const list = [1, 2, 3] const fn = (x: number) => [`${x}`, `${x}`] describe('R.chain', () => { it('without passing type', () => { const result = chain(fn, list) result // $ExpectType string[] const curriedResult = chain(fn)(list) curriedResult // $ExpectType string[] }) })

    ---------------

    clamp

    Restrict a number input to be within min and max limits.

    If input is bigger than max, then the result is max.

    If input is smaller than min, then the result is min.

    const result = [
      R.clamp(0, 10, 5), 
      R.clamp(0, 10, -1),
      R.clamp(0, 10, 11)
    ]
    // => [5, 0, 10]
    

    Try this R.clamp example in Rambda REPL

    ---------------

    clone

    It creates a deep copy of the input, which may contain (nested) Arrays and Objects, Numbers, Strings, Booleans and Dates.

    const objects = [{a: 1}, {b: 2}];
    const objectsClone = R.clone(objects);
    
    const result = [
      R.equals(objects, objectsClone),
      R.equals(objects[0], objectsClone[0]),
    ] // => [ true, true ]
    

    Try this R.clone example in Rambda REPL

    ---------------

    complement

    It returns inverted version of origin function that accept input as argument.

    The return value of inverted is the negative boolean value of origin(input).

    const origin = x => x > 5
    const inverted = complement(origin)
    
    const result = [
      origin(7),
      inverted(7)
    ] => [ true, false ]
    

    Try this R.complement example in Rambda REPL

    ---------------

    compose

    It performs right-to-left function composition.

    const result = R.compose(
      R.map(x => x * 2),
      R.filter(x => x > 2)
    )([1, 2, 3, 4])
    
    // => [6, 8]
    

    Try this R.compose example in Rambda REPL

    ---------------

    concat

    It returns a new string or array, which is the result of merging x and y.

    R.concat([1, 2])([3, 4]) // => [1, 2, 3, 4]
    R.concat('foo', 'bar') // => 'foobar'
    

    Try this R.concat example in Rambda REPL

    ---------------

    cond

    It takes list with conditions and returns a new function fn that expects input as argument.

    This function will start evaluating the conditions in order to find the first winner(order of conditions matter).

    The winner is this condition, which left side returns true when input is its argument. Then the evaluation of the right side of the winner will be the final result.

    If no winner is found, then fn returns undefined.

    const fn = R.cond([
      [ x => x > 25, R.always('more than 25') ],
      [ x => x > 15, R.always('more than 15') ],
      [ R.T, x => `${x} is nothing special` ],
    ])
    
    const result = [
      fn(30),
      fn(20),
      fn(10),
    ] 
    // => ['more than 25', 'more than 15', '10 is nothing special']
    

    Try this R.cond example in Rambda REPL

    ---------------

    converge

    Accepts a converging function and a list of branching functions and returns a new function. When invoked, this new function is applied to some arguments, each branching function is applied to those same arguments. The results of each branching function are passed as arguments to the converging function to produce the return value.

    :boom: Explanation is taken from Ramda documentation

    const result = R.converge(R.multiply)([ R.add(1), R.add(3) ])(2)
    // => 15
    

    Try this R.converge example in Rambda REPL

    ---------------

    count

    It counts how many times predicate function returns true, when supplied with iteration of list.

    const list = [{a: 1}, 1, {a:2}]
    const result = R.count(x => x.a !== undefined, list)
    // => 2
    

    Try this R.count example in Rambda REPL

    ---------------

    countBy

    
    countBy<T extends unknown>(transformFn: (x: T) => any, list: T[]): Record<string, number>
    

    It counts elements in a list after each instance of the input list is passed through transformFn function.

    const list = [ 'a', 'A', 'b', 'B', 'c', 'C' ]
    
    const result = countBy(R.toLower, list)
    const expected = { a: 2, b: 2, c: 2 }
    // => `result` is equal to `expected`
    

    Try this R.countBy example in Rambda REPL

    All Typescript definitions typescript countBy<T extends unknown>(transformFn: (x: T) => any, list: T[]): Record<string, number>; countBy<T extends unknown>(transformFn: (x: T) => any): (list: T[]) => Record<string, number>;
    R.countBy source javascript export function countBy(fn, list){ if (arguments.length === 1){ return _list => countBy(fn, _list) } const willReturn = {} list.forEach(item => { const key = fn(item) if (!willReturn[ key ]){ willReturn[ key ] = 1 } else { willReturn[ key ]++ } }) return willReturn }
    Tests javascript import { countBy } from './countBy.js' const list = [ 'a', 'A', 'b', 'B', 'c', 'C' ] test('happy', () => { const result = countBy(x => x.toLowerCase(), list) expect(result).toEqual({ a : 2, b : 2, c : 2, }) })
    Typescript test typescript import { countBy } from 'rambda' const transformFn = (x: string) => x.toLowerCase() const list = [ 'a', 'A', 'b', 'B', 'c', 'C' ] describe('R.countBy', () => { it('happy', () => { const result = countBy(transformFn, list) result // $ExpectType Record<string, number> }) it('curried', () => { const result = countBy(transformFn)(list) result // $ExpectType Record<string, number> }) })

    ---------------

    curry

    It expects a function as input and returns its curried version.

    const fn = (a, b, c) => a + b + c
    const curried = R.curry(fn)
    const sum = curried(1,2)
    
    const result = sum(3) // => 6
    

    Try this R.curry example in Rambda REPL

    ---------------

    curryN

    It returns a curried equivalent of the provided function, with the specified arity.

    ---------------

    dec

    It decrements a number.

    ---------------

    defaultTo

    
    defaultTo<T>(defaultValue: T, input: T | null | undefined): T
    

    It returns defaultValue, if all of inputArguments are undefined, null or NaN.

    Else, it returns the first truthy inputArguments instance(from left to right).

    :boom: Rambda's defaultTo accept indefinite number of arguments when non curried, i.e. R.defaultTo(2, foo, bar, baz).

    R.defaultTo('foo', 'bar') // => 'bar'
    R.defaultTo('foo', undefined) // => 'foo'
    
    // Important - emtpy string is not falsy value(same as Ramda)
    R.defaultTo('foo', '') // => 'foo'
    

    Try this R.defaultTo example in Rambda REPL

    All Typescript definitions typescript defaultTo<T>(defaultValue: T, input: T | null | undefined): T; defaultTo<T>(defaultValue: T): (input: T | null | undefined) => T;
    R.defaultTo source javascript function isFalsy(input){ return ( input === undefined || input === null || Number.isNaN(input) === true ) } export function defaultTo(defaultArgument, input){ if (arguments.length === 1){ return _input => defaultTo(defaultArgument, _input) } return isFalsy(input) ? defaultArgument : input }
    Tests javascript import {defaultTo} from './defaultTo.js' test('with undefined', () => { expect(defaultTo('foo')(undefined)).toEqual('foo') }) test('with null', () => { expect(defaultTo('foo')(null)).toEqual('foo') }) test('with NaN', () => { expect(defaultTo('foo')(NaN)).toEqual('foo') }) test('with empty string', () => { expect(defaultTo('foo', '')).toEqual('') }) test('with false', () => { expect(defaultTo('foo', false)).toBeFalse() }) test('when inputArgument passes initial check', () => { expect(defaultTo('foo', 'bar')).toEqual('bar') })
    Typescript test typescript import {defaultTo} from 'rambda' describe('R.defaultTo with Ramda spec', () => { it('happy', () => { const result = defaultTo('foo', '') result // $ExpectType "" | "foo" }) it('with explicit type', () => { const result = defaultTo<string>('foo', null) result // $ExpectType string }) })
    Rambda is faster than Ramda with 48.91% text const R = require('../../dist/rambda.js') const input = [ null, undefined, 5 ] const defaultTo = [ { label : 'Rambda', fn : () => { R.defaultTo(3, input[ 0 ]) }, }, { label : 'Ramda', fn : () => { Ramda.defaultTo(3, input[ 0 ]) }, }, { label : 'Rambda with multiple arguments', fn : () => { R.defaultTo(3, ...input) }, }, ]

    ---------------

    difference

    
    difference<T>(a: T[], b: T[]): T[]
    

    It returns the uniq set of all elements in the first list a not contained in the second list b.

    R.equals is used to determine equality.

    const a = [ 1, 2, 3, 4 ]
    const b = [ 3, 4, 5, 6 ]
    
    const result = difference(a, b)
    // => [ 1, 2 ]
    

    Try this R.difference example in Rambda REPL

    All Typescript definitions typescript difference<T>(a: T[], b: T[]): T[]; difference<T>(a: T[]): (b: T[]) => T[];
    R.difference source javascript import { includes } from './includes.js' import { uniq } from './uniq.js' export function difference(a, b){ if (arguments.length === 1) return _b => difference(a, _b) return uniq(a).filter(aInstance => !includes(aInstance, b)) }
    Tests javascript import { difference as differenceRamda } from 'ramda' import { difference } from './difference.js' test('difference', () => { const a = [ 1, 2, 3, 4 ] const b = [ 3, 4, 5, 6 ] expect(difference(a)(b)).toEqual([ 1, 2 ]) expect(difference([], [])).toEqual([]) }) test('difference with objects', () => { const a = [ { id : 1 }, { id : 2 }, { id : 3 }, { id : 4 } ] const b = [ { id : 3 }, { id : 4 }, { id : 5 }, { id : 6 } ] expect(difference(a, b)).toEqual([ { id : 1 }, { id : 2 } ]) }) test('no duplicates in first list', () => { const M2 = [ 1, 2, 3, 4, 1, 2, 3, 4 ] const N2 = [ 3, 3, 4, 4, 5, 5, 6, 6 ] expect(difference(M2, N2)).toEqual([ 1, 2 ]) }) test('should use R.equals', () => { expect(difference([ 1 ], [ 1 ]).length).toEqual(0) expect(differenceRamda([ NaN ], [ NaN ]).length).toEqual(0) })
    Typescript test typescript import {difference} from 'rambda' const list1 = [1, 2, 3] const list2 = [1, 2, 4] describe('R.difference', () => { it('happy', () => { const result = difference(list1, list2) result // $ExpectType number[] }) it('curried', () => { const result = difference(list1)(list2) result // $ExpectType number[] }) })

    ---------------

    dissoc

    It returns a new object that does not contain property prop.

    R.dissoc('b', {a: 1, b: 2, c: 3})
    // => {a: 1, c: 3}
    

    Try this R.dissoc example in Rambda REPL

    ---------------

    divide

    R.divide(71, 100) // => 0.71
    

    Try this R.divide example in Rambda REPL

    ---------------

    drop

    
    drop<T>(howMany: number, input: T[]): T[]
    

    It returns howMany items dropped from beginning of list or string input.

    R.drop(2, ['foo', 'bar', 'baz']) // => ['baz']
    R.drop(2, 'foobar')  // => 'obar'
    

    Try this R.drop example in Rambda REPL

    All Typescript definitions typescript drop<T>(howMany: number, input: T[]): T[]; drop(howMany: number, input: string): string; drop<T>(howMany: number): { <T>(input: T[]): T[]; (input: string): string; };
    R.drop source javascript export function drop(howManyToDrop, listOrString){ if (arguments.length === 1) return _list => drop(howManyToDrop, _list) return listOrString.slice(howManyToDrop > 0 ? howManyToDrop : 0) }
    Tests javascript import assert from 'assert' import { drop } from './drop.js' test('with array', () => { expect(drop(2)([ 'foo', 'bar', 'baz' ])).toEqual([ 'baz' ]) expect(drop(3, [ 'foo', 'bar', 'baz' ])).toEqual([]) expect(drop(4, [ 'foo', 'bar', 'baz' ])).toEqual([]) }) test('with string', () => { expect(drop(3, 'rambda')).toEqual('bda') }) test('with non-positive count', () => { expect(drop(0, [ 1, 2, 3 ])).toEqual([ 1, 2, 3 ]) expect(drop(-1, [ 1, 2, 3 ])).toEqual([ 1, 2, 3 ]) expect(drop(-Infinity, [ 1, 2, 3 ])).toEqual([ 1, 2, 3 ]) }) test('should return copy', () => { const xs = [ 1, 2, 3 ] assert.notStrictEqual(drop(0, xs), xs) assert.notStrictEqual(drop(-1, xs), xs) })
    Typescript test typescript import {drop} from 'rambda' const list = [1, 2, 3, 4] const str = 'foobar' const howMany = 2 describe('R.drop - array', () => { it('happy', () => { const result = drop(howMany, list) result // $ExpectType number[] }) it('curried', () => { const result = drop(howMany)(list) result // $ExpectType number[] }) }) describe('R.drop - string', () => { it('happy', () => { const result = drop(howMany, str) result // $ExpectType string }) it('curried', () => { const result = drop(howMany)(str) result // $ExpectType string }) })
    Rambda is faster than Ramda with 82.35% text const R = require('../../dist/rambda.js') const input = [ 1, 2, 3, 4 ] const drop = [ { label : 'Rambda', fn : () => { R.drop(3, input) }, }, { label : 'Ramda', fn : () => { Ramda.drop(3, input) }, }, ]

    ---------------

    dropLast

    
    dropLast<T>(howMany: number, input: T[]): T[]
    

    It returns howMany items dropped from the end of list or string input.

    R.dropLast(2, ['foo', 'bar', 'baz']) // => ['foo']
    R.dropLast(2, 'foobar')  // => 'foob'
    

    Try this R.dropLast example in Rambda REPL

    All Typescript definitions typescript dropLast<T>(howMany: number, input: T[]): T[]; dropLast(howMany: number, input: string): string; dropLast<T>(howMany: number): { <T>(input: T[]): T[]; (input: string): string; };
    R.dropLast source javascript export function dropLast(howManyToDrop, listOrString){ if (arguments.length === 1){ return _listOrString => dropLast(howManyToDrop, _listOrString) } return howManyToDrop > 0 ? listOrString.slice(0, -howManyToDrop) : listOrString.slice() }
    Tests javascript import assert from 'assert' import { dropLast } from './dropLast.js' test('with array', () => { expect(dropLast(2)([ 'foo', 'bar', 'baz' ])).toEqual([ 'foo' ]) expect(dropLast(3, [ 'foo', 'bar', 'baz' ])).toEqual([]) expect(dropLast(4, [ 'foo', 'bar', 'baz' ])).toEqual([]) }) test('with string', () => { expect(dropLast(3, 'rambda')).toEqual('ram') }) test('with non-positive count', () => { expect(dropLast(0, [ 1, 2, 3 ])).toEqual([ 1, 2, 3 ]) expect(dropLast(-1, [ 1, 2, 3 ])).toEqual([ 1, 2, 3 ]) expect(dropLast(-Infinity, [ 1, 2, 3 ])).toEqual([ 1, 2, 3 ]) }) test('should return copy', () => { const xs = [ 1, 2, 3 ] assert.notStrictEqual(dropLast(0, xs), xs) assert.notStrictEqual(dropLast(-1, xs), xs) })
    Typescript test typescript import {dropLast} from 'rambda' const list = [1, 2, 3, 4] const str = 'foobar' const howMany = 2 describe('R.dropLast - array', () => { it('happy', () => { const result = dropLast(howMany, list) result // $ExpectType number[] }) it('curried', () => { const result = dropLast(howMany)(list) result // $ExpectType number[] }) }) describe('R.dropLast - string', () => { it('happy', () => { const result = dropLast(howMany, str) result // $ExpectType string }) it('curried', () => { const result = dropLast(howMany)(str) result // $ExpectType string }) })
    Rambda is faster than Ramda with 86.74% text const R = require('../../dist/rambda.js') const input = [ 1, 2, 3, 4 ] const dropLast = [ { label : 'Rambda', fn : () => { R.dropLast(3, input) }, }, { label : 'Ramda', fn : () => { Ramda.dropLast(3, input) }, }, ]

    ---------------

    dropLastWhile

    const list = [1, 2, 3, 4, 5];
    const predicate = x => x >= 3
    
    const result = dropLastWhile(predicate, list);
    // => [1, 2]
    

    Try this R.dropLastWhile example in Rambda REPL

    ---------------

    dropRepeats

    
    dropRepeats<T>(list: T[]): T[]
    

    It removes any successive duplicates according to R.equals.

    const result = R.dropRepeats([
      1, 
      1, 
      {a: 1}, 
      {a:1}, 
      1
    ])
    // => [1, {a: 1}, 1]
    

    Try this R.dropRepeats example in Rambda REPL

    All Typescript definitions typescript dropRepeats<T>(list: T[]): T[];
    R.dropRepeats source javascript import { _isArray } from './_internals/_isArray.js' import { equals } from './equals.js' export function dropRepeats(list){ if (!_isArray(list)){ throw new Error(`${ list } is not a list`) } const toReturn = [] list.reduce((prev, current) => { if (!equals(prev, current)){ toReturn.push(current) } return current }, undefined) return toReturn }
    Tests javascript import { dropRepeats as dropRepeatsRamda } from 'ramda' import { compareCombinations } from './_internals/testUtils.js' import { add } from './add.js' import { dropRepeats } from './dropRepeats.js' const list = [ 1, 2, 2, 2, 3, 4, 4, 5, 5, 3, 2, 2, { a : 1 }, { a : 1 } ] const listClean = [ 1, 2, 3, 4, 5, 3, 2, { a : 1 } ] test('happy', () => { const result = dropRepeats(list) expect(result).toEqual(listClean) }) const possibleLists = [ [ add(1), async () => {}, [ 1 ], [ 1 ], [ 2 ], [ 2 ] ], [ add(1), add(1), add(2) ], [], 1, /foo/g, Promise.resolve(1), ] describe('brute force', () => { compareCombinations({ firstInput : possibleLists, callback : errorsCounters => { expect(errorsCounters).toMatchInlineSnapshot(` Object { "ERRORS_MESSAGE_MISMATCH": 0, "ERRORS_TYPE_MISMATCH": 0, "RESULTS_MISMATCH": 1, "SHOULD_NOT_THROW": 3, "SHOULD_THROW": 0, "TOTAL_TESTS": 6, } `) }, fn : dropRepeats, fnRamda : dropRepeatsRamda, }) })
    Typescript test typescript import {dropRepeats} from 'rambda' describe('R.dropRepeats', () => { it('happy', () => { const result = dropRepeats([1, 2, 2, 3]) result // $ExpectType number[] }) })

    ---------------

    dropRepeatsWith

    const list = [{a:1,b:2}, {a:1,b:3}, {a:2, b:4}]
    const result = R.dropRepeatsWith(R.prop('a'), list)
    
    // => [{a:1,b:2}, {a:2, b:4}]
    

    Try this R.dropRepeatsWith example in Rambda REPL

    ---------------

    dropWhile

    const list = [1, 2, 3, 4]
    const predicate = x => x < 3
    const result = R.dropWhile(predicate, list)
    // => [3, 4]
    

    Try this R.dropWhile example in Rambda REPL

    ---------------

    either

    
    either(firstPredicate: Pred, secondPredicate: Pred): Pred
    

    It returns a new predicate function from firstPredicate and secondPredicate inputs.

    This predicate function will return true, if any of the two input predicates return true.

    const firstPredicate = x => x > 10
    const secondPredicate = x => x % 2 === 0
    const predicate = R.either(firstPredicate, secondPredicate)
    
    const result = [
      predicate(15),
      predicate(8),
      predicate(7),
    ]
    // => [true, true, false]
    

    Try this R.either example in Rambda REPL

    All Typescript definitions typescript either(firstPredicate: Pred, secondPredicate: Pred): Pred; either<T>(firstPredicate: Predicate<T>, secondPredicate: Predicate<T>): Predicate<T>; either<T>(firstPredicate: Predicate<T>): (secondPredicate: Predicate<T>) => Predicate<T>; either(firstPredicate: Pred): (secondPredicate: Pred) => Pred;
    R.either source javascript export function either(firstPredicate, secondPredicate){ if (arguments.length === 1){ return _secondPredicate => either(firstPredicate, _secondPredicate) } return (...input) => Boolean(firstPredicate(...input) || secondPredicate(...input)) }
    Tests javascript import { either } from './either.js' test('with multiple inputs', () => { const between = function ( a, b, c ){ return a < b && b < c } const total20 = function ( a, b, c ){ return a + b + c === 20 } const fn = either(between, total20) expect(fn( 7, 8, 5 )).toBeTrue() }) test('skip evaluation of the second expression', () => { let effect = 'not evaluated' const F = function (){ return true } const Z = function (){ effect = 'Z got evaluated' } either(F, Z)() expect(effect).toBe('not evaluated') }) test('case 1', () => { const firstFn = val => val > 0 const secondFn = val => val * 5 > 10 expect(either(firstFn, secondFn)(1)).toBeTrue() }) test('case 2', () => { const firstFn = val => val > 0 const secondFn = val => val === -10 const fn = either(firstFn)(secondFn) expect(fn(-10)).toBeTrue() })
    Typescript test typescript import {either} from 'rambda' describe('R.either', () => { it('with passed type', () => { const fn = either<number>( x => x > 1, x => x % 2 === 0 ) fn // $ExpectType Predicate<number> const result = fn(2) // $ExpectType boolean result // $ExpectType boolean }) it('with passed type - curried', () => { const fn = either<number>(x => x > 1)(x => x % 2 === 0) fn // $ExpectType Predicate<number> const result = fn(2) result // $ExpectType boolean }) it('no type passed', () => { const fn = either( x => { x // $ExpectType any return x > 1 }, x => { x // $ExpectType any return x % 2 === 0 } ) const result = fn(2) result // $ExpectType boolean }) it('no type passed - curried', () => { const fn = either((x: number) => { x // $ExpectType number return x > 1 })((x: number) => { x // $ExpectType number return x % 2 === 0 }) const result = fn(2) result // $ExpectType boolean }) })

    ---------------

    endsWith

    
    endsWith(target: string, iterable: string): boolean
    

    When iterable is a string, then it behaves as String.prototype.endsWith. When iterable is a list, then it uses R.equals to determine if the target list ends in the same way as the given target.

    const str = 'foo-bar'
    const list = [{a:1}, {a:2}, {a:3}]
    
    const result = [
      R.endsWith('bar', str),
      R.endsWith([{a:1}, {a:2}], list)
    ]
    // => [true, true]
    

    Try this R.endsWith example in Rambda REPL

    All Typescript definitions typescript endsWith(target: string, iterable: string): boolean; endsWith(target: string): (iterable: string) => boolean; endsWith<T>(target: T[], list: T[]): boolean; endsWith<T>(target: T[]): (list: T[]) => boolean;
    R.endsWith source javascript import { _isArray } from './_internals/_isArray.js' import { equals } from './equals.js' export function endsWith(target, iterable){ if (arguments.length === 1) return _iterable => endsWith(target, _iterable) if (typeof iterable === 'string'){ return iterable.endsWith(target) } if (!_isArray(target)) return false const diff = iterable.length - target.length let correct = true const filtered = target.filter((x, index) => { if (!correct) return false const result = equals(x, iterable[ index + diff ]) if (!result) correct = false return result }) return filtered.length === target.length }
    Tests javascript import { endsWith as endsWithRamda } from 'ramda' import { compareCombinations } from './_internals/testUtils.js' import { endsWith } from './endsWith.js' test('with string', () => { expect(endsWith('bar', 'foo-bar')).toBeTrue() expect(endsWith('baz')('foo-bar')).toBeFalse() }) test('use R.equals with array', () => { const list = [ { a : 1 }, { a : 2 }, { a : 3 } ] expect(endsWith({ a : 3 }, list)).toBeFalse(), expect(endsWith([ { a : 3 } ], list)).toBeTrue() expect(endsWith([ { a : 2 }, { a : 3 } ], list)).toBeTrue() expect(endsWith(list, list)).toBeTrue() expect(endsWith([ { a : 1 } ], list)).toBeFalse() }) export const possibleTargets = [ NaN, [ NaN ], /foo/, [ /foo/ ], Promise.resolve(1), [ Promise.resolve(1) ], Error('foo'), [ Error('foo') ], ] export const possibleIterables = [ [ Promise.resolve(1), Promise.resolve(2) ], [ /foo/, /bar/ ], [ NaN ], [ Error('foo'), Error('bar') ], ] describe('brute force', () => { compareCombinations({ fn : endsWith, fnRamda : endsWithRamda, firstInput : possibleTargets, secondInput : possibleIterables, callback : errorsCounters => { expect(errorsCounters).toMatchInlineSnapshot(` Object { "ERRORS_MESSAGE_MISMATCH": 0, "ERRORS_TYPE_MISMATCH": 0, "RESULTS_MISMATCH": 0, "SHOULD_NOT_THROW": 0, "SHOULD_THROW": 0, "TOTAL_TESTS": 32, } `) }, }) })
    Typescript test typescript import {endsWith} from 'rambda' describe('R.endsWith - array as iterable', () => { const target = [{a: 2}] const iterable = [{a: 1}, {a: 2}] it('happy', () => { const result = endsWith(target, iterable) result // $ExpectType boolean }) it('curried', () => { const result = endsWith(target)(iterable) result // $ExpectType boolean }) }) describe('R.endsWith - string as iterable', () => { const target = 'bar' const iterable = 'foo bar' it('happy', () => { const result = endsWith(target, iterable) result // $ExpectType boolean }) it('curried', () => { const result = endsWith(target)(iterable) result // $ExpectType boolean }) })

    ---------------

    eqProps

    It returns true if property prop in obj1 is equal to property prop in obj2 according to R.equals.

    const obj1 = {a: 1, b:2}
    const obj2 = {a: 1, b:3}
    const result = R.eqProps('a', obj1, obj2)
    // => true
    

    Try this R.eqProps example in Rambda REPL

    ---------------

    equals

    
    equals<T>(x: T, y: T): boolean
    

    It deeply compares x and y and returns true if they are equal.

    :boom: It doesn't handle cyclical data structures and functions

    R.equals(
      [1, {a:2}, [{b: 3}]],
      [1, {a:2}, [{b: 3}]]
    ) // => true
    

    Try this R.equals example in Rambda REPL

    All Typescript definitions typescript equals<T>(x: T, y: T): boolean; equals<T>(x: T): (y: T) => boolean;
    R.equals source javascript import { _isArray } from './_internals/_isArray.js' import { type } from './type.js' export function _lastIndexOf(valueToFind, list){ if (!_isArray(list)){ throw new Error(`Cannot read property 'indexOf' of ${ list }`) } const typeOfValue = type(valueToFind) if (![ 'Object', 'Array', 'NaN', 'RegExp' ].includes(typeOfValue)) return list.lastIndexOf(valueToFind) const { length } = list let index = length let foundIndex = -1 while (--index > -1 && foundIndex === -1){ if (equals(list[ index ], valueToFind)){ foundIndex = index } } return foundIndex } export function _indexOf(valueToFind, list){ if (!_isArray(list)){ throw new Error(`Cannot read property 'indexOf' of ${ list }`) } const typeOfValue = type(valueToFind) if (![ 'Object', 'Array', 'NaN', 'RegExp' ].includes(typeOfValue)) return list.indexOf(valueToFind) let index = -1 let foundIndex = -1 const { length } = list while (++index < length && foundIndex === -1){ if (equals(list[ index ], valueToFind)){ foundIndex = index } } return foundIndex } function _arrayFromIterator(iter){ const list = [] let next while (!(next = iter.next()).done){ list.push(next.value) } return list } function _equalsSets(a, b){ if (a.size !== b.size){ return false } const aList = _arrayFromIterator(a.values()) const bList = _arrayFromIterator(b.values()) const filtered = aList.filter(aInstance => _indexOf(aInstance, bList) === -1) return filtered.length === 0 } function parseError(maybeError){ const typeofError = maybeError.__proto__.toString() if (![ 'Error', 'TypeError' ].includes(typeofError)) return [] return [ typeofError, maybeError.message ] } function parseDate(maybeDate){ if (!maybeDate.toDateString) return [ false ] return [ true, maybeDate.getTime() ] } function parseRegex(maybeRegex){ if (maybeRegex.constructor !== RegExp) return [ false ] return [ true, maybeRegex.toString() ] } function equalsSets(a, b){ if (a.size !== b.size){ return false } const aList = _arrayFromIterator(a.values()) const bList = _arrayFromIterator(b.values()) const filtered = aList.filter(aInstance => _indexOf(aInstance, bList) === -1) return filtered.length === 0 } export function equals(a, b){ if (arguments.length === 1) return _b => equals(a, _b) const aType = type(a) if (aType !== type(b)) return false if (aType === 'Function'){ return a.name === undefined ? false : a.name === b.name } if ([ 'NaN', 'Undefined', 'Null' ].includes(aType)) return true if (aType === 'Number'){ if (Object.is(-0, a) !== Object.is(-0, b)) return false return a.toString() === b.toString() } if ([ 'String', 'Boolean' ].includes(aType)){ return a.toString() === b.toString() } if (aType === 'Array'){ const aClone = Array.from(a) const bClone = Array.from(b) if (aClone.toString() !== bClone.toString()){ return false } let loopArrayFlag = true aClone.forEach((aCloneInstance, aCloneIndex) => { if (loopArrayFlag){ if ( aCloneInstance !== bClone[ aCloneIndex ] && !equals(aCloneInstance, bClone[ aCloneIndex ]) ){ loopArrayFlag = false } } }) return loopArrayFlag } const aRegex = parseRegex(a) const bRegex = parseRegex(b) if (aRegex[ 0 ]){ return bRegex[ 0 ] ? aRegex[ 1 ] === bRegex[ 1 ] : false } else if (bRegex[ 0 ]) return false const aDate = parseDate(a) const bDate = parseDate(b) if (aDate[ 0 ]){ return bDate[ 0 ] ? aDate[ 1 ] === bDate[ 1 ] : false } else if (bDate[ 0 ]) return false const aError = parseError(a) const bError = parseError(b) if (aError[ 0 ]){ return bError[ 0 ] ? aError[ 0 ] === bError[ 0 ] && aError[ 1 ] === bError[ 1 ] : false } if (aType === 'Set'){ return _equalsSets(a, b) } if (aType === 'Object'){ const aKeys = Object.keys(a) if (aKeys.length !== Object.keys(b).length){ return false } let loopObjectFlag = true aKeys.forEach(aKeyInstance => { if (loopObjectFlag){ const aValue = a[ aKeyInstance ] const bValue = b[ aKeyInstance ] if (aValue !== bValue && !equals(aValue, bValue)){ loopObjectFlag = false } } }) return loopObjectFlag } return false }
    Tests javascript import {equals as equalsRamda} from 'ramda' import {compareCombinations} from './_internals/testUtils.js' import {variousTypes} from './benchmarks/_utils.js' import {equals} from './equals.js' test('compare functions', () => { function foo() {} function bar() {} const baz = () => {} const expectTrue = equals(foo, foo) const expectFalseFirst = equals(foo, bar) const expectFalseSecond = equals(foo, baz) expect(expectTrue).toBeTrue() expect(expectFalseFirst).toBeFalse() expect(expectFalseSecond).toBeFalse() }) test('with array of objects', () => { const list1 = [{a: 1}, [{b: 2}]] const list2 = [{a: 1}, [{b: 2}]] const list3 = [{a: 1}, [{b: 3}]] expect(equals(list1, list2)).toBeTrue() expect(equals(list1, list3)).toBeFalse() }) test('with regex', () => { expect(equals(/s/, /s/)).toBeTrue() expect(equals(/s/, /d/)).toBeFalse() expect(equals(/a/gi, /a/gi)).toBeTrue() expect(equals(/a/gim, /a/gim)).toBeTrue() expect(equals(/a/gi, /a/i)).toBeFalse() }) test('not a number', () => { expect(equals([NaN], [NaN])).toBeTrue() }) test('new number', () => { expect(equals(new Number(0), new Number(0))).toBeTrue() expect(equals(new Number(0), new Number(1))).toBeFalse() expect(equals(new Number(1), new Number(0))).toBeFalse() }) test('new string', () => { expect(equals(new String(''), new String(''))).toBeTrue() expect(equals(new String(''), new String('x'))).toBeFalse() expect(equals(new String('x'), new String(''))).toBeFalse() expect(equals(new String('foo'), new String('foo'))).toBeTrue() expect(equals(new String('foo'), new String('bar'))).toBeFalse() expect(equals(new String('bar'), new String('foo'))).toBeFalse() }) test('new Boolean', () => { expect(equals(new Boolean(true), new Boolean(true))).toBeTrue() expect(equals(new Boolean(false), new Boolean(false))).toBeTrue() expect(equals(new Boolean(true), new Boolean(false))).toBeFalse() expect(equals(new Boolean(false), new Boolean(true))).toBeFalse() }) test('new Error', () => { expect(equals(new Error('XXX'), {})).toBeFalse() expect(equals(new Error('XXX'), new TypeError('XXX'))).toBeFalse() expect(equals(new Error('XXX'), new Error('YYY'))).toBeFalse() expect(equals(new Error('XXX'), new Error('XXX'))).toBeTrue() expect(equals(new Error('XXX'), new TypeError('YYY'))).toBeFalse() }) test('with dates', () => { expect(equals(new Date(0), new Date(0))).toBeTrue() expect(equals(new Date(1), new Date(1))).toBeTrue() expect(equals(new Date(0), new Date(1))).toBeFalse() expect(equals(new Date(1), new Date(0))).toBeFalse() expect(equals(new Date(0), {})).toBeFalse() expect(equals({}, new Date(0))).toBeFalse() }) test('ramda spec', () => { expect(equals({}, {})).toBeTrue() expect( equals( { a: 1, b: 2, }, { a: 1, b: 2, } ) ).toBeTrue() expect( equals( { a: 2, b: 3, }, { b: 3, a: 2, } ) ).toBeTrue() expect( equals( { a: 2, b: 3, }, { a: 3, b: 3, } ) ).toBeFalse() expect( equals( { a: 2, b: 3, c: 1, }, { a: 2, b: 3, } ) ).toBeFalse() }) test('works with boolean tuple', () => { expect(equals([true, false], [true, false])).toBeTrue() expect(equals([true, false], [true, true])).toBeFalse() }) test('works with equal objects within array', () => { const objFirst = { a: { b: 1, c: 2, d: [1], }, } const objSecond = { a: { b: 1, c: 2, d: [1], }, } const x = [1, 2, objFirst, null, '', []] const y = [1, 2, objSecond, null, '', []] expect(equals(x, y)).toBeTrue() }) test('works with different objects within array', () => { const objFirst = {a: {b: 1}} const objSecond = {a: {b: 2}} const x = [1, 2, objFirst, null, '', []] const y = [1, 2, objSecond, null, '', []] expect(equals(x, y)).toBeFalse() }) test('works with undefined as second argument', () => { expect(equals(1, undefined)).toBeFalse() expect(equals(undefined, undefined)).toBeTrue() }) test('compare sets', () => { const toCompareDifferent = new Set([{a: 1}, {a: 2}]) const toCompareSame = new Set([{a: 1}, {a: 2}, {a: 1}]) const testSet = new Set([{a: 1}, {a: 2}, {a: 1}]) expect(equals(toCompareSame, testSet)).toBeTruthy() expect(equals(toCompareDifferent, testSet)).toBeFalsy() expect(equalsRamda(toCompareSame, testSet)).toBeTruthy() expect(equalsRamda(toCompareDifferent, testSet)).toBeFalsy() }) test('compare simple sets', () => { const testSet = new Set(['2', '3', '3', '2', '1']) expect(equals(new Set(['3', '2', '1']), testSet)).toBeTruthy() expect(equals(new Set(['3', '2', '0']), testSet)).toBeFalsy() }) test('various examples', () => { expect(equals([1, 2, 3])([1, 2, 3])).toBeTrue() expect(equals([1, 2, 3], [1, 2])).toBeFalse() expect(equals(1, 1)).toBeTrue() expect(equals(1, '1')).toBeFalse() expect(equals({}, {})).toBeTrue() expect( equals( { a: 1, b: 2, }, { b: 2, a: 1, } ) ).toBeTrue() expect( equals( { a: 1, b: 2, }, { a: 1, b: 1, } ) ).toBeFalse() expect( equals( { a: 1, b: false, }, { a: 1, b: 1, } ) ).toBeFalse() expect( equals( { a: 1, b: 2, }, { b: 2, a: 1, c: 3, } ) ).toBeFalse() expect( equals( { x: { a: 1, b: 2, }, }, { x: { b: 2, a: 1, c: 3, }, } ) ).toBeFalse() expect( equals( { a: 1, b: 2, }, { b: 3, a: 1, } ) ).toBeFalse() expect(equals({a: {b: {c: 1}}}, {a: {b: {c: 1}}})).toBeTrue() expect(equals({a: {b: {c: 1}}}, {a: {b: {c: 2}}})).toBeFalse() expect(equals({a: {}}, {a: {}})).toBeTrue() expect(equals('', '')).toBeTrue() expect(equals('foo', 'foo')).toBeTrue() expect(equals('foo', 'bar')).toBeFalse() expect(equals(0, false)).toBeFalse() expect(equals(/\s/g, null)).toBeFalse() expect(equals(null, null)).toBeTrue() expect(equals(false)(null)).toBeFalse() }) test('with custom functions', () => { function foo() { return 1 } foo.prototype.toString = () => '' const result = equals(foo, foo) expect(result).toBeTrue() }) test('with classes', () => { class Foo {} const foo = new Foo() const result = equals(foo, foo) expect(result).toBeTrue() }) test('with negative zero', () => { expect(equals(-0, -0)).toBeTrue() expect(equals(-0, 0)).toBeFalse() expect(equals(0, 0)).toBeTrue() expect(equals(-0, 1)).toBeFalse() }) const possibleInputs = variousTypes describe('brute force', () => { compareCombinations({ fn: equals, fnRamda: equalsRamda, firstInput: possibleInputs, secondInput: possibleInputs, callback: errorsCounters => { expect(errorsCounters).toMatchInlineSnapshot(` Object { "ERRORS_MESSAGE_MISMATCH": 0, "ERRORS_TYPE_MISMATCH": 0, "RESULTS_MISMATCH": 5, "SHOULD_NOT_THROW": 4, "SHOULD_THROW": 0, "TOTAL_TESTS": 289, } `) }, }) })
    Typescript test typescript import {equals} from 'rambda' describe('R.equals', () => { it('happy', () => { const result = equals(4, 1) result // $ExpectType boolean }) it('with object', () => { const foo = {a: 1} const bar = {a: 2} const result = equals(foo, bar) result // $ExpectType boolean }) it('curried', () => { const result = equals(4)(1) result // $ExpectType boolean }) })
    Lodash is fastest. Rambda is 58.37% slower and Ramda is 96.73% slower text const R = require('../../dist/rambda.js') const limit = 10000 const strings = Array(limit) .fill(null) .map(() => Math.floor(Math.random() * 1000)) const equals = [ { label : 'Rambda', fn : () => { strings.forEach(x => R.equals(x, 'ss')) }, }, { label : 'Ramda', fn : () => { strings.forEach(x => Ramda.equals(x, 'ss')) }, }, { label : 'Lodash', fn : () => { strings.forEach(x => _.isEqual(x, 'ss')) }, }, ]

    ---------------

    evolve

    
    evolve<T, U>(rules: ((x: T) => U)[], list: T[]): U[]
    

    It takes object or array of functions as set of rules. These rules are applied to the iterable input to produce the result.

    :boom: Error handling of this method differs between Ramda and Rambda. Ramda for some wrong inputs returns result and for other - it returns one of the inputs. Rambda simply throws when inputs are not correct. Full details for this mismatch are listed in source/_snapshots/evolve.spec.js.snap file.

    const rules = {
      foo : add(1),
      bar : add(-1),
    }
    const input = {
      a   : 1,
      foo : 2,
      bar : 3,
    }
    const result = evolve(rules, input)
    const expected = {
      a   : 1,
      foo : 3,
      bar : 2,
    })
    // => `result` is equal to `expected`
    

    Try this R.evolve example in Rambda REPL

    All Typescript definitions typescript evolve<T, U>(rules: ((x: T) => U)[], list: T[]): U[]; evolve<T, U>(rules: ((x: T) => U)[]) : (list: T[]) => U[]; evolve<E extends Evolver, V extends Evolvable<E>>(rules: E, obj: V): Evolve<V, E>; evolve<E extends Evolver>(rules: E): <V extends Evolvable<E>>(obj: V) => Evolve<V, E>;
    R.evolve source javascript import { _isArray } from './_internals/_isArray.js' import { mapArray, mapObject } from './map.js' import { type } from './type.js' export function evolveArray(rules, list){ return mapArray( (x, i) => { if (type(rules[ i ]) === 'Function'){ return rules[ i ](x) } return x }, list, true ) } export function evolveObject(rules, iterable){ return mapObject((x, prop) => { if (type(x) === 'Object'){ const typeRule = type(rules[ prop ]) if (typeRule === 'Function'){ return rules[ prop ](x) } if (typeRule === 'Object'){ return evolve(rules[ prop ], x) } return x } if (type(rules[ prop ]) === 'Function'){ return rules[ prop ](x) } return x }, iterable) } export function evolve(rules, iterable){ if (arguments.length === 1){ return _iterable => evolve(rules, _iterable) } const rulesType = type(rules) const iterableType = type(iterable) if (iterableType !== rulesType){ throw new Error('iterableType !== rulesType') } if (![ 'Object', 'Array' ].includes(rulesType)){ throw new Error(`'iterable' and 'rules' are from wrong type ${ rulesType }`) } if (iterableType === 'Object'){ return evolveObject(rules, iterable) } return evolveArray(rules, iterable) }
    Tests javascript import { evolve as evolveRamda } from 'ramda' import { add } from '../rambda.js' import { compareCombinations, compareToRamda } from './_internals/testUtils.js' import { evolve } from './evolve.js' test('happy', () => { const rules = { foo : add(1), nested : { bar : x => Object.keys(x).length }, } const input = { a : 1, foo : 2, nested : { bar : { z : 3 } }, } const result = evolve(rules, input) expect(result).toEqual({ a : 1, foo : 3, nested : { bar : 1 }, }) }) test('nested rule is wrong', () => { const rules = { foo : add(1), nested : { bar : 10 }, } const input = { a : 1, foo : 2, nested : { bar : { z : 3 } }, } const result = evolve(rules)(input) expect(result).toEqual({ a : 1, foo : 3, nested : { bar : { z : 3 } }, }) }) test('is recursive', () => { const rules = { nested : { second : add(-1), third : add(1), }, } const object = { first : 1, nested : { second : 2, third : 3, }, } const expected = { first : 1, nested : { second : 1, third : 4, }, } const result = evolve(rules, object) expect(result).toEqual(expected) }) test('ignores primitive values', () => { const rules = { n : 2, m : 'foo', } const object = { n : 0, m : 1, } const expected = { n : 0, m : 1, } const result = evolve(rules, object) expect(result).toEqual(expected) }) test('with array', () => { const rules = [ add(1), add(-1) ] const list = [ 100, 1400 ] const expected = [ 101, 1399 ] const result = evolve(rules, list) expect(result).toEqual(expected) }) const rulesObject = { a : add(1) } const rulesList = [ add(1) ] const possibleIterables = [ null, undefined, '', 42, [], [ 1 ], { a : 1 } ] const possibleRules = [ ...possibleIterables, rulesList, rulesObject ] describe('brute force', () => { compareCombinations({ firstInput : possibleRules, callback : errorsCounters => { expect(errorsCounters).toMatchInlineSnapshot(` Object { "ERRORS_MESSAGE_MISMATCH": 0, "ERRORS_TYPE_MISMATCH": 4, "RESULTS_MISMATCH": 0, "SHOULD_NOT_THROW": 51, "SHOULD_THROW": 0, "TOTAL_TESTS": 63, } `) }, secondInput : possibleIterables, fn : evolve, fnRamda : evolveRamda, }) })
    Typescript test typescript import {evolve, add} from 'rambda' describe('R.evolve', () => { it('happy', () => { const input = { foo: 2, nested: { a: 1, bar: 3, }, } const rules = { foo: add(1), nested: { a: add(-1), bar: add(1), }, } const result = evolve(rules, input) const curriedResult = evolve(rules)(input) result.nested.a // $ExpectType number curriedResult.nested.a // $ExpectType number result.nested.bar // $ExpectType number result.foo // $ExpectType number }) it('with array', () => { const rules = [String, String] const input = [100, 1400] const result = evolve(rules, input) const curriedResult = evolve(rules)(input) result // $ExpectType string[] curriedResult // $ExpectType string[] }) })

    ---------------

    F

    
    F(): boolean
    
    F() // => false
    

    Try this R.F example in Rambda REPL

    All Typescript definitions typescript F(): boolean;
    R.F source javascript export function F(){ return false }

    ---------------

    filter

    
    filter<T>(predicate: Predicate<T>): (input: T[]) => T[]
    

    It filters list or object input using a predicate function.

    const list = [3, 4, 3, 2]
    const listPredicate = x => x > 2
    
    const object = {abc: 'fo', xyz: 'bar', baz: 'foo'}
    const objectPredicate = (x, prop) => x.length + prop.length > 5
    
    const result = [
      R.filter(listPredicate, list),
      R.filter(objectPredicate, object)
    ]
    // => [ [3, 4], { xyz: 'bar', baz: 'foo'} ]
    

    Try this R.filter example in Rambda REPL

    All Typescript definitions typescript filter<T>(predicate: Predicate<T>): (input: T[]) => T[]; filter<T>(predicate: Predicate<T>, input: T[]): T[]; filter<T, U>(predicate: ObjectPredicate<T>): (x: Dictionary<T>) => Dictionary<T>; filter<T>(predicate: ObjectPredicate<T>, x: Dictionary<T>): Dictionary<T>;
    R.filter source javascript import { _isArray } from './_internals/_isArray.js' export function filterObject(predicate, obj){ const willReturn = {} for (const prop in obj){ if (predicate( obj[ prop ], prop, obj )){ willReturn[ prop ] = obj[ prop ] } } return willReturn } export function filterArray( predicate, list, indexed = false ){ let index = 0 const len = list.length const willReturn = [] while (index < len){ const predicateResult = indexed ? predicate(list[ index ], index) : predicate(list[ index ]) if (predicateResult){ willReturn.push(list[ index ]) } index++ } return willReturn } export function filter(predicate, iterable){ if (arguments.length === 1) return _iterable => filter(predicate, _iterable) if (!iterable){ throw new Error('Incorrect iterable input') } if (_isArray(iterable)) return filterArray( predicate, iterable, false ) return filterObject(predicate, iterable) }
    Tests javascript import { filter as filterRamda } from 'ramda' import { filter } from './filter.js' import { T } from './T.js' const sampleObject = { a : 1, b : 2, c : 3, d : 4, } test('happy', () => { const isEven = n => n % 2 === 0 expect(filter(isEven, [ 1, 2, 3, 4 ])).toEqual([ 2, 4 ]) expect(filter(isEven, { a : 1, b : 2, d : 3, })).toEqual({ b : 2 }) }) test('predicate when input is object', () => { const obj = { a : 1, b : 2, } const predicate = ( val, prop, inputObject ) => { expect(inputObject).toEqual(obj) expect(typeof prop).toEqual('string') return val < 2 } expect(filter(predicate, obj)).toEqual({ a : 1 }) }) test('with object', () => { const isEven = n => n % 2 === 0 const result = filter(isEven, sampleObject) const expectedResult = { b : 2, d : 4, } expect(result).toEqual(expectedResult) }) test('bad inputs difference between Ramda and Rambda', () => { expect(() => filter(T, null)).toThrowWithMessage(Error, 'Incorrect iterable input') expect(() => filter(T)(undefined)).toThrowWithMessage(Error, 'Incorrect iterable input') expect(() => filterRamda(T, null)).toThrowWithMessage(TypeError, 'Cannot read properties of null (reading \'fantasy-land/filter\')') expect(() => filterRamda(T, undefined)).toThrowWithMessage(TypeError, 'Cannot read properties of undefined (reading \'fantasy-land/filter\')') })
    Typescript test typescript import {filter} from 'rambda' const list = [1, 2, 3] const obj = {a: 1, b: 2} describe('R.filter with array', () => { it('happy', () => { const result = filter<number>(x => { x // $ExpectType number return x > 1 }, list) result // $ExpectType number[] }) it('curried', () => { const result = filter<number>(x => { x // $ExpectType number return x > 1 })(list) result // $ExpectType number[] }) }) describe('R.filter with objects', () => { it('happy', () => { const result = filter<number>((val, prop, origin) => { val // $ExpectType number prop // $ExpectType string origin // $ExpectType Dictionary<number> return val > 1 }, obj) result // $ExpectType Dictionary<number> }) it('curried version requires second dummy type', () => { const result = filter<number, any>((val, prop, origin) => { val // $ExpectType number prop // $ExpectType string origin // $ExpectType Dictionary<number> return val > 1 })(obj) result // $ExpectType Dictionary<number> }) })
    Lodash is fastest. Rambda is 6.7% slower and Ramda is 72.03% slower text const R = require('../../dist/rambda.js') const arr = [ 1, 2, 3, 4 ] const fn = x => x > 2 const filter = [ { label : 'Rambda', fn : () => { R.filter(fn, arr) }, }, { label : 'Ramda', fn : () => { Ramda.filter(fn, arr) }, }, { label : 'Lodash', fn : () => { _.filter(arr, fn) }, }, ]

    ---------------

    find

    
    find<T>(predicate: (x: T) => boolean, list: T[]): T | undefined
    

    It returns the first element of list that satisfy the predicate.

    If there is no such element, it returns undefined.

    const predicate = x => R.type(x.foo) === 'Number'
    const list = [{foo: 'bar'}, {foo: 1}]
    
    const result = R.find(predicate, list)
    // => {foo: 1}
    

    Try this R.find example in Rambda REPL

    All Typescript definitions typescript find<T>(predicate: (x: T) => boolean, list: T[]): T | undefined; find<T>(predicate: (x: T) => boolean): (list: T[]) => T | undefined;
    R.find source javascript export function find(predicate, list){ if (arguments.length === 1) return _list => find(predicate, _list) let index = 0 const len = list.length while (index < len){ const x = list[ index ] if (predicate(x)){ return x } index++ } }
    Tests javascript import { find } from './find.js' import { propEq } from './propEq.js' const list = [ { a : 1 }, { a : 2 }, { a : 3 } ] test('happy', () => { const fn = propEq('a', 2) expect(find(fn, list)).toEqual({ a : 2 }) }) test('with curry', () => { const fn = propEq('a', 4) expect(find(fn)(list)).toBeUndefined() }) test('with empty list', () => { expect(find(() => true, [])).toBeUndefined() })
    Typescript test typescript import {find} from 'rambda' const list = [1, 2, 3] describe('R.find', () => { it('happy', () => { const predicate = (x: number) => x > 2 const result = find(predicate, list) result // $ExpectType number | undefined }) it('curried', () => { const predicate = (x: number) => x > 2 const result = find(predicate)(list) result // $ExpectType number | undefined }) })
    Rambda is fastest. Ramda is 85.14% slower and Lodash is 42.65% slower text const R = require('../../dist/rambda.js') const fn = x => x > 2 const list = [ 1, 2, 3, 4 ] const find = [ { label : 'Rambda', fn : () => { R.find(fn, list) }, }, { label : 'Ramda', fn : () => { Ramda.find(fn, list) }, }, { label : 'Lodash', fn : () => { _.find(list, fn) }, }, ]

    ---------------

    findIndex

    
    findIndex<T>(predicate: (x: T) => boolean, list: T[]): number
    

    It returns the index of the first element of list satisfying the predicate function.

    If there is no such element, then -1 is returned.

    const predicate = x => R.type(x.foo) === 'Number'
    const list = [{foo: 'bar'}, {foo: 1}]
    
    const result = R.findIndex(predicate, list)
    // => 1
    

    Try this R.findIndex example in Rambda REPL

    All Typescript definitions typescript findIndex<T>(predicate: (x: T) => boolean, list: T[]): number; findIndex<T>(predicate: (x: T) => boolean): (list: T[]) => number;
    R.findIndex source javascript export function findIndex(predicate, list){ if (arguments.length === 1) return _list => findIndex(predicate, _list) const len = list.length let index = -1 while (++index < len){ if (predicate(list[ index ])){ return index } } return -1 }
    Tests javascript import { findIndex } from './findIndex.js' import { propEq } from './propEq.js' const list = [ { a : 1 }, { a : 2 }, { a : 3 } ] test('happy', () => { expect(findIndex(propEq('a', 2), list)).toEqual(1) expect(findIndex(propEq('a', 1))(list)).toEqual(0) expect(findIndex(propEq('a', 4))(list)).toEqual(-1) })
    Typescript test typescript import {findIndex} from 'rambda' const list = [1, 2, 3] describe('R.findIndex', () => { it('happy', () => { const predicate = (x: number) => x > 2 const result = findIndex(predicate, list) result // $ExpectType number }) it('curried', () => { const predicate = (x: number) => x > 2 const result = findIndex(predicate)(list) result // $ExpectType number }) })
    Rambda is fastest. Ramda is 86.48% slower and Lodash is 72.27% slower text const R = require('../../dist/rambda.js') const fn = x => x > 2 const list = [ 1, 2, 3, 4 ] const findIndex = [ { label : 'Rambda', fn : () => { R.findIndex(fn, list) }, }, { label : 'Ramda', fn : () => { Ramda.findIndex(fn, list) }, }, { label : 'Lodash', fn : () => { _.findIndex(list, fn) }, }, ]

    ---------------

    findLast

    
    findLast<T>(fn: (x: T) => boolean, list: T[]): T | undefined
    

    It returns the last element of list satisfying the predicate function.

    If there is no such element, then undefined is returned.

    const predicate = x => R.type(x.foo) === 'Number'
    const list = [{foo: 0}, {foo: 1}]
    
    const result = R.findLast(predicate, list)
    // => {foo: 1}
    

    Try this R.findLast example in Rambda REPL

    All Typescript definitions typescript findLast<T>(fn: (x: T) => boolean, list: T[]): T | undefined; findLast<T>(fn: (x: T) => boolean): (list: T[]) => T | undefined;
    R.findLast source javascript export function findLast(predicate, list){ if (arguments.length === 1) return _list => findLast(predicate, _list) let index = list.length while (--index >= 0){ if (predicate(list[ index ])){ return list[ index ] } } return undefined }
    Tests javascript import { findLast } from './findLast.js' test('happy', () => { const result = findLast(x => x > 1, [ 1, 1, 1, 2, 3, 4, 1 ]) expect(result).toEqual(4) expect(findLast(x => x === 0, [ 0, 1, 1, 2, 3, 4, 1 ])).toEqual(0) }) test('with curry', () => { expect(findLast(x => x > 1)([ 1, 1, 1, 2, 3, 4, 1 ])).toEqual(4) }) const obj1 = { x : 100 } const obj2 = { x : 200 } const a = [ 11, 10, 9, 'cow', obj1, 8, 7, 100, 200, 300, obj2, 4, 3, 2, 1, 0 ] const even = function (x){ return x % 2 === 0 } const gt100 = function (x){ return x > 100 } const isStr = function (x){ return typeof x === 'string' } const xGt100 = function (o){ return o && o.x > 100 } test('ramda 1', () => { expect(findLast(even, a)).toEqual(0) expect(findLast(gt100, a)).toEqual(300) expect(findLast(isStr, a)).toEqual('cow') expect(findLast(xGt100, a)).toEqual(obj2) }) test('ramda 2', () => { expect(findLast(even, [ 'zing' ])).toEqual(undefined) }) test('ramda 3', () => { expect(findLast(even, [ 2, 3, 5 ])).toEqual(2) }) test('ramda 4', () => { expect(findLast(even, [])).toEqual(undefined) })
    Typescript test typescript import {findLast} from 'rambda' const list = [1, 2, 3] describe('R.findLast', () => { it('happy', () => { const predicate = (x: number) => x > 2 const result = findLast(predicate, list) result // $ExpectType number | undefined }) it('curried', () => { const predicate = (x: number) => x > 2 const result = findLast(predicate)(list) result // $ExpectType number | undefined }) })

    ---------------

    findLastIndex

    
    findLastIndex<T>(predicate: (x: T) => boolean, list: T[]): number
    

    It returns the index of the last element of list satisfying the predicate function.

    If there is no such element, then -1 is returned.

    const predicate = x => R.type(x.foo) === 'Number'
    const list = [{foo: 0}, {foo: 1}]
    
    const result = R.findLastIndex(predicate, list)
    // => 1
    

    Try this R.findLastIndex example in Rambda REPL

    All Typescript definitions typescript findLastIndex<T>(predicate: (x: T) => boolean, list: T[]): number; findLastIndex<T>(predicate: (x: T) => boolean): (list: T[]) => number;
    R.findLastIndex source javascript export function findLastIndex(fn, list){ if (arguments.length === 1) return _list => findLastIndex(fn, _list) let index = list.length while (--index >= 0){ if (fn(list[ index ])){ return index } } return -1 }
    Tests javascript import { findLastIndex } from './findLastIndex.js' test('happy', () => { const result = findLastIndex(x => x > 1, [ 1, 1, 1, 2, 3, 4, 1 ]) expect(result).toEqual(5) expect(findLastIndex(x => x === 0, [ 0, 1, 1, 2, 3, 4, 1 ])).toEqual(0) }) test('with curry', () => { expect(findLastIndex(x => x > 1)([ 1, 1, 1, 2, 3, 4, 1 ])).toEqual(5) }) const obj1 = { x : 100 } const obj2 = { x : 200 } const a = [ 11, 10, 9, 'cow', obj1, 8, 7, 100, 200, 300, obj2, 4, 3, 2, 1, 0 ] const even = function (x){ return x % 2 === 0 } const gt100 = function (x){ return x > 100 } const isStr = function (x){ return typeof x === 'string' } const xGt100 = function (o){ return o && o.x > 100 } test('ramda 1', () => { expect(findLastIndex(even, a)).toEqual(15) expect(findLastIndex(gt100, a)).toEqual(9) expect(findLastIndex(isStr, a)).toEqual(3) expect(findLastIndex(xGt100, a)).toEqual(10) }) test('ramda 2', () => { expect(findLastIndex(even, [ 'zing' ])).toEqual(-1) }) test('ramda 3', () => { expect(findLastIndex(even, [ 2, 3, 5 ])).toEqual(0) }) test('ramda 4', () => { expect(findLastIndex(even, [])).toEqual(-1) })
    Typescript test typescript import {findLastIndex} from 'rambda' const list = [1, 2, 3] describe('R.findLastIndex', () => { it('happy', () => { const predicate = (x: number) => x > 2 const result = findLastIndex(predicate, list) result // $ExpectType number }) it('curried', () => { const predicate = (x: number) => x > 2 const result = findLastIndex(predicate)(list) result // $ExpectType number }) })

    ---------------

    flatten

    
    flatten<T>(list: any[]): T[]
    

    It deeply flattens an array.

    const result = R.flatten([
      1, 
      2, 
      [3, 30, [300]], 
      [4]
    ])
    // => [ 1, 2, 3, 30, 300, 4 ]
    

    Try this R.flatten example in Rambda REPL

    All Typescript definitions typescript flatten<T>(list: any[]): T[];
    R.flatten source javascript import { _isArray } from './_internals/_isArray.js' export function flatten(list, input){ const willReturn = input === undefined ? [] : input for (let i = 0; i < list.length; i++){ if (_isArray(list[ i ])){ flatten(list[ i ], willReturn) } else { willReturn.push(list[ i ]) } } return willReturn }
    Tests javascript import { flatten } from './flatten.js' test('happy', () => { expect(flatten([ 1, 2, 3, [ [ [ [ [ 4 ] ] ] ] ] ])).toEqual([ 1, 2, 3, 4 ]) expect(flatten([ 1, [ 2, [ [ 3 ] ] ], [ 4 ] ])).toEqual([ 1, 2, 3, 4 ]) expect(flatten([ 1, [ 2, [ [ [ 3 ] ] ] ], [ 4 ] ])).toEqual([ 1, 2, 3, 4 ]) expect(flatten([ 1, 2, [ 3, 4 ], 5, [ 6, [ 7, 8, [ 9, [ 10, 11 ], 12 ] ] ] ])).toEqual([ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 ]) }) test('readme example', () => { const result = flatten([ 1, 2, [ 3, 30, [ 300 ] ], [ 4 ] ]) expect(result).toEqual([ 1, 2, 3, 30, 300, 4 ]) })
    Typescript test typescript import {flatten} from 'rambda' describe('flatten', () => { it('happy', () => { const result = flatten<number>([1, 2, [3, [4]]]) result // $ExpectType number[] }) })
    Rambda is fastest. Ramda is 95.26% slower and Lodash is 10.27% slower text const R = require('../../dist/rambda.js') const list = [ 1, [ 2, [ 3, 4, 6 ] ] ] const flatten = [ { label : 'Rambda', fn : () => { R.flatten(list) }, }, { label : 'Ramda', fn : () => { Ramda.flatten(list) }, }, { label : 'Lodash', fn : () => { _.flatten(list) }, }, ]

    ---------------

    flip

    It returns function which calls fn with exchanged first and second argument.

    :boom: Rambda's flip will throw if the arity of the input function is greater or equal to 5.

    const subtractFlip = R.flip(R.subtract)
    
    const result = [
      subtractFlip(1,7),
      R.subtract(1, 6)
    ]  
    // => [6, -6]
    

    Try this R.flip example in Rambda REPL

    ---------------

    forEach

    
    forEach<T>(fn: Iterator<T, void>, list: T[]): T[]
    

    It applies iterable function over all members of list and returns list.

    :boom: It works with objects, unlike Ramda.

    const sideEffect = {}
    const result = R.forEach(
      x => sideEffect[`foo${x}`] = x
    )([1, 2])
    
    sideEffect // => {foo1: 1, foo2: 2}
    result // => [1, 2]
    

    Try this R.forEach example in Rambda REPL

    All Typescript definitions typescript forEach<T>(fn: Iterator<T, void>, list: T[]): T[]; forEach<T>(fn: Iterator<T, void>): (list: T[]) => T[]; forEach<T>(fn: ObjectIterator<T, void>, list: Dictionary<T>): Dictionary<T>; forEach<T, U>(fn: ObjectIterator<T, void>): (list: Dictionary<T>) => Dictionary<T>;
    R.forEach source javascript import { _isArray } from './_internals/_isArray.js' import { _keys } from './_internals/_keys.js' export function forEach(fn, list){ if (arguments.length === 1) return _list => forEach(fn, _list) if (list === undefined){ return } if (_isArray(list)){ let index = 0 const len = list.length while (index < len){ fn(list[ index ]) index++ } } else { let index = 0 const keys = _keys(list) const len = keys.length while (index < len){ const key = keys[ index ] fn( list[ key ], key, list ) index++ } } return list }
    Tests javascript import { forEach } from './forEach.js' import { type } from './type.js' test('happy', () => { const sideEffect = {} forEach(x => sideEffect[ `foo${ x }` ] = x + 10)([ 1, 2 ]) expect(sideEffect).toEqual({ foo1 : 11, foo2 : 12, }) }) test('iterate over object', () => { const obj = { a : 1, b : [ 1, 2 ], c : { d : 7 }, f : 'foo', } const result = {} const returned = forEach(( val, prop, inputObj ) => { expect(type(inputObj)).toBe('Object') result[ prop ] = `${ prop }-${ type(val) }` })(obj) const expected = { a : 'a-Number', b : 'b-Array', c : 'c-Object', f : 'f-String', } expect(result).toEqual(expected) expect(returned).toEqual(obj) }) test('with empty list', () => { const list = [] const result = forEach(x => x * x)(list) expect(result).toEqual(list) }) test('with wrong input', () => { const list = undefined const result = forEach(x => x * x)(list) expect(result).toBeUndefined() }) test('returns the input', () => { const list = [ 1, 2, 3 ] const result = forEach(x => x * x)(list) expect(result).toEqual(list) })
    Typescript test typescript import {forEach} from 'rambda' const list = [1, 2, 3] const obj = {a: 1, b: 2} describe('R.forEach with arrays', () => { it('happy', () => { const result = forEach(a => { a // $ExpectType number }, list) result // $ExpectType number[] }) it('curried require an explicit typing', () => { const result = forEach<number>(a => { a // $ExpectType number })(list) result // $ExpectType number[] }) }) describe('R.forEach with objects', () => { it('happy', () => { const result = forEach((a, b, c) => { a // $ExpectType number b // $ExpectType string c // $ExpectType Dictionary<number> return `${a}` }, obj) result // $ExpectType Dictionary<number> }) it('curried require an input typing and a dummy third typing', () => { // Required in order all typings to work const result = forEach<number, any>((a, b, c) => { a // $ExpectType number b // $ExpectType string c // $ExpectType Dictionary<number> })(obj) result // $ExpectType Dictionary<number> }) it('iterator without property', () => { const result = forEach(a => { a // $ExpectType number }, obj) result // $ExpectType Dictionary<number> }) })

    ---------------

    fromPairs

    It transforms a listOfPairs to an object.

    const listOfPairs = [ [ 'a', 1 ], [ 'b', 2 ], [ 'c', [ 3, 4 ] ] ]
    const expected = {
      a : 1,
      b : 2,
      c : [ 3, 4 ],
    }
    
    const result = R.fromPairs(listOfPairs)
    // => `result` is equal to `expected`
    

    Try this R.fromPairs example in Rambda REPL

    ---------------

    groupBy

    It splits list according to a provided groupFn function and returns an object.

    const list = [ 'a', 'b', 'aa', 'bb' ]
    const groupFn = x => x.length
    
    const result = R.groupBy(groupFn, list)
    // => { '1': ['a', 'b'], '2': ['aa', 'bb'] }
    

    Try this R.groupBy example in Rambda REPL

    ---------------

    groupWith

    It returns separated version of list or string input, where separation is done with equality compareFn function.

    const compareFn = (x, y) => x === y
    const list = [1, 2, 2, 1, 1, 2]
    
    const result = R.groupWith(isConsecutive, list)
    // => [[1], [2,2], [1,1], [2]]
    

    Try this R.groupWith example in Rambda REPL

    ---------------

    has

    
    has<T>(prop: string, obj: T): boolean
    

    It returns true if obj has property prop.

    const obj = {a: 1}
    
    const result = [
      R.has('a', Record<string, unknown>),
      R.has('b', Record<string, unknown>)
    ]
    // => [true, false]
    

    Try this R.has example in Rambda REPL

    All Typescript definitions typescript has<T>(prop: string, obj: T): boolean; has(prop: string): <T>(obj: T) => boolean;
    R.has source javascript export function has(prop, obj){ if (arguments.length === 1) return _obj => has(prop, _obj) if (!obj) return false return obj.hasOwnProperty(prop) }
    Tests javascript import {has} from './has.js' test('happy', () => { expect(has('a')({a: 1})).toBeTrue() expect(has('b', {a: 1})).toBeFalse() }) test('with non-object', () => { expect(has('a', undefined)).toBeFalse() expect(has('a', null)).toBeFalse() expect(has('a', true)).toBeFalse() expect(has('a', '')).toBeFalse() expect(has('a', /a/)).toBeFalse() })
    Typescript test typescript import {has} from 'rambda' describe('R.has', () => { it('happy', () => { const result = has('foo', {a: 1}) const curriedResult = has('bar')({a: 1}) result // $ExpectType boolean curriedResult // $ExpectType boolean }) })

    ---------------

    hasPath

    
    hasPath<T>(
      path: string | string[],
      input: object
    ): boolean
    

    It will return true, if input object has truthy path(calculated with R.path).

    const path = 'a.b'
    const pathAsArray = ['a', 'b']
    const obj = {a: {b: []}}
    
    const result = [
      R.hasPath(path, Record<string, unknown>),
      R.hasPath(pathAsArray, Record<string, unknown>),
      R.hasPath('a.c', Record<string, unknown>),
    ]
    // => [true, true, false]
    

    Try this R.hasPath example in Rambda REPL

    All Typescript definitions typescript hasPath<T>( path: string | string[], input: object ): boolean; hasPath<T>( path: string | string[] ): (input: object) => boolean;
    R.hasPath source javascript import { path } from './path.js' export function hasPath(pathInput, obj){ if (arguments.length === 1){ return objHolder => hasPath(pathInput, objHolder) } return path(pathInput, obj) !== undefined }
    Tests javascript import { hasPath } from './hasPath.js' test('when true', () => { const path = 'a.b' const obj = { a : { b : [] } } const result = hasPath(path)(obj) const expectedResult = true expect(result).toEqual(expectedResult) }) test('when false', () => { const path = 'a.b' const obj = {} const result = hasPath(path, obj) const expectedResult = false expect(result).toEqual(expectedResult) })
    Typescript test typescript import {hasPath} from 'rambda' describe('R.hasPath', () => { it('string path', () => { const obj = {a: {b: 1}} const result = hasPath('a.b', obj) const curriedResult = hasPath('a.c')(obj) result // $ExpectType boolean curriedResult // $ExpectType boolean }) it('array path', () => { const obj = {a: {b: 1}} const result = hasPath(['a', 'b'], obj) const curriedResult = hasPath(['a', 'c'])(obj) result // $ExpectType boolean curriedResult // $ExpectType boolean }) })

    ---------------

    
    head(input: string): string
    

    It returns the first element of list or string input.

    const result = [
      R.head([1, 2, 3]),
      R.head('foo') 
    ]
    // => [1, 'f']
    

    Try this R.head example in Rambda REPL

    All Typescript definitions typescript head(input: string): string; head(emptyList: []): undefined; head<T>(input: T[]): T | undefined;
    R.head source javascript export function head(listOrString){ if (typeof listOrString === 'string') return listOrString[ 0 ] || '' return listOrString[ 0 ] }
    Tests javascript import { head } from './head.js' test('head', () => { expect(head([ 'fi', 'fo', 'fum' ])).toEqual('fi') expect(head([])).toEqual(undefined) expect(head('foo')).toEqual('f') expect(head('')).toEqual('') })
    Typescript test typescript import {head} from 'rambda' describe('R.head', () => { it('string', () => { const result = head('foo') result // $ExpectType string }) it('array', () => { const result = head([1, 2, 3]) result // $ExpectType number | undefined }) it('empty array - case 1', () => { const result = head([]) result // $ExpectType undefined }) it('empty array - case 2', () => { const list = ['foo', 'bar'].filter(x => x.startsWith('a')) const result = head(list) result // $ExpectType string | undefined }) })

    ---------------

    identical

    It returns true if its arguments a and b are identical.

    Otherwise, it returns false.

    :boom: Values are identical if they reference the same memory. NaN is identical to NaN; 0 and -0 are not identical.

    const objA = {a: 1};
    const objB = {a: 1};
    R.identical(objA, objA); // => true
    R.identical(objA, objB); // => false
    R.identical(1, 1); // => true
    R.identical(1, '1'); // => false
    R.identical([], []); // => false
    R.identical(0, -0); // => false
    R.identical(NaN, NaN); // => true
    

    Try this R.identical example in Rambda REPL

    ---------------

    identity

    
    identity<T>(input: T): T
    

    It just passes back the supplied input argument.

    :boom: Logic

    R.identity(7) // => 7
    

    Try this R.identity example in Rambda REPL

    All Typescript definitions typescript identity<T>(input: T): T;
    R.identity source javascript export function identity(x){ return x }
    Tests javascript import {identity} from './identity.js' test('happy', () => { expect(identity(7)).toEqual(7) expect(identity(true)).toBeTrue() expect(identity({a: 1})).toEqual({a: 1}) })
    Typescript test typescript import {identity} from 'rambda' describe('R.identity', () => { it('happy', () => { const result = identity(4) result // $ExpectType 4 }) })

    ---------------

    ifElse

    
    ifElse<TArgs extends any[], TOnTrueResult, TOnFalseResult>(fn: (...args: TArgs) => boolean, onTrue: (...args: TArgs) => TOnTrueResult, onFalse: (...args: TArgs) => TOnFalseResult): (...args: TArgs) => TOnTrueResult | TOnFalseResult
    

    It expects condition, onTrue and onFalse functions as inputs and it returns a new function with example name of fn.

    When fn`` is called withinputargument, it will return eitheronTrue(input)oronFalse(input)depending oncondition(input)` evaluation.

    const fn = R.ifElse(
     x => x>10,
     x => x*2,
     x => x*10
    )
    
    const result = [ fn(8), fn(18) ]
    // => [80, 36]
    

    Try this R.ifElse example in Rambda REPL

    All Typescript definitions typescript ifElse<TArgs extends any[], TOnTrueResult, TOnFalseResult>(fn: (...args: TArgs) => boolean, onTrue: (...args: TArgs) => TOnTrueResult, onFalse: (...args: TArgs) => TOnFalseResult): (...args: TArgs) => TOnTrueResult | TOnFalseResult;
    R.ifElse source javascript import { curry } from './curry.js' function ifElseFn( condition, onTrue, onFalse ){ return (...input) => { const conditionResult = typeof condition === 'boolean' ? condition : condition(...input) if (conditionResult === true){ return onTrue(...input) } return onFalse(...input) } } export const ifElse = curry(ifElseFn)
    Tests javascript import {always} from './always.js' import {has} from './has.js' import {identity} from './identity.js' import {ifElse} from './ifElse.js' import {prop} from './prop.js' const condition = has('foo') const v = function (a) { return typeof a === 'number' } const t = function (a) { return a + 1 } const ifFn = x => prop('foo', x).length const elseFn = () => false test('happy', () => { const fn = ifElse(condition, ifFn)(elseFn) expect(fn({foo: 'bar'})).toEqual(3) expect(fn({fo: 'bar'})).toBeFalse() }) test('ramda spec', () => { const ifIsNumber = ifElse(v) expect(ifIsNumber(t, identity)(15)).toEqual(16) expect(ifIsNumber(t, identity)('hello')).toEqual('hello') }) test('pass all arguments', () => { const identity = function (a) { return a } const v = function () { return true } const onTrue = function (a, b) { expect(a).toEqual(123) expect(b).toEqual('abc') } ifElse(v, onTrue, identity)(123, 'abc') }) test('accept constant as condition', () => { const fn = ifElse(true)(always(true))(always(false)) expect(fn()).toBeTrue() }) test('accept constant as condition - case 2', () => { const fn = ifElse(false, always(true), always(false)) expect(fn()).toBeFalse() }) test('curry 1', () => { const fn = ifElse(condition, ifFn)(elseFn) expect(fn({foo: 'bar'})).toEqual(3) expect(fn({fo: 'bar'})).toBeFalse() }) test('curry 2', () => { const fn = ifElse(condition)(ifFn)(elseFn) expect(fn({foo: 'bar'})).toEqual(3) expect(fn({fo: 'bar'})).toBeFalse() }) test('simple arity of 1', () => { const condition = x => x > 5 const onTrue = x => x + 1 const onFalse = x => x + 10 const result = ifElse(condition, onTrue, onFalse)(1) expect(result).toBe(11) }) test('simple arity of 2', () => { const condition = (x, y) => x + y > 5 const onTrue = (x, y) => x + y + 1 const onFalse = (x, y) => x + y + 10 const result = ifElse(condition, onTrue, onFalse)(1, 10) expect(result).toBe(12) })
    Typescript test typescript import {ifElse} from 'rambda' describe('R.ifElse', () => { it('happy', () => { const condition = (x: number) => x > 5 const onTrue = (x: number) => `foo${x}` const onFalse = (x: number) => `bar${x}` const fn = ifElse(condition, onTrue, onFalse) fn // $ExpectType (x: number) => string const result = fn(3) result // $ExpectType string }) it('arity of 2', () => { const condition = (x: number, y: string) => x + y.length > 5 const onTrue = (x: number, y: string) => `foo${x}-${y}` const onFalse = (x: number, y: string) => `bar${x}-${y}` const fn = ifElse(condition, onTrue, onFalse) fn // $ExpectType (x: number, y: string) => string const result = fn(3, 'hello') result // $ExpectType string }) })
    Rambda is faster than Ramda with 58.56% text const R = require('../../dist/rambda.js') const condition = R.has('foo') const v = function (a){ return typeof a === 'number' } const t = function (a){ return a + 1 } const ifFn = x => R.prop('foo', x).length const elseFn = () => false const ifElse = [ { label : 'Rambda', fn : () => { const fn = R.ifElse(condition, ifFn)(elseFn) fn({ foo : 'bar' }) fn({ fo : 'bar' }) const ifIsNumber = R.ifElse(v) ifIsNumber(t, R.identity)(15) ifIsNumber(t, R.identity)('hello') }, }, { label : 'Ramda', fn : () => { const fn = Ramda.ifElse(condition, ifFn)(elseFn) fn({ foo : 'bar' }) fn({ fo : 'bar' }) const ifIsNumber = Ramda.ifElse(v) ifIsNumber(t, R.identity)(15) ifIsNumber(t, R.identity)('hello') }, }, ]

    ---------------

    inc

    It increments a number.

    R.inc(1) // => 2
    

    Try this R.inc example in Rambda REPL

    ---------------

    includes

    
    includes(valueToFind: string, input: string[] | string): boolean
    

    If input is string, then this method work as native String.includes.

    If input is array, then R.equals is used to define if valueToFind belongs to the list.

    const result = [
      R.includes('oo', 'foo'),
      R.includes({a: 1}, [{a: 1}])
    ]
    // => [true, true ]
    

    Try this R.includes example in Rambda REPL

    All Typescript definitions typescript includes(valueToFind: string, input: string[] | string): boolean; includes(valueToFind: string): (input: string[] | string) => boolean; includes<T>(valueToFind: T, input: T[]): boolean; includes<T>(valueToFind: T): (input: T[]) => boolean;
    R.includes source javascript import { _isArray } from './_internals/_isArray.js' import { _indexOf } from './equals.js' export function includes(valueToFind, iterable){ if (arguments.length === 1) return _iterable => includes(valueToFind, _iterable) if (typeof iterable === 'string'){ return iterable.includes(valueToFind) } if (!iterable){ throw new TypeError(`Cannot read property \'indexOf\' of ${ iterable }`) } if (!_isArray(iterable)) return false return _indexOf(valueToFind, iterable) > -1 }
    Tests javascript import { includes as includesRamda } from 'ramda' import { includes } from './includes.js' test('with string as iterable', () => { const str = 'foo bar' expect(includes('bar')(str)).toBeTrue() expect(includesRamda('bar')(str)).toBeTrue() expect(includes('never', str)).toBeFalse() expect(includesRamda('never', str)).toBeFalse() }) test('with array as iterable', () => { const arr = [ 1, 2, 3 ] expect(includes(2)(arr)).toBeTrue() expect(includesRamda(2)(arr)).toBeTrue() expect(includes(4, arr)).toBeFalse() expect(includesRamda(4, arr)).toBeFalse() }) test('with list of objects as iterable', () => { const arr = [ { a : 1 }, { b : 2 }, { c : 3 } ] expect(includes({ c : 3 }, arr)).toBeTrue() expect(includesRamda({ c : 3 }, arr)).toBeTrue() }) test('with NaN', () => { const result = includes(NaN, [ NaN ]) const ramdaResult = includesRamda(NaN, [ NaN ]) expect(result).toBeTrue() expect(ramdaResult).toBeTrue() }) test('with wrong input that does not throw', () => { const result = includes(1, /foo/g) const ramdaResult = includesRamda(1, /foo/g) expect(result).toBeFalse() expect(ramdaResult).toBeFalse() }) test('throws on wrong input - match ramda behaviour', () => { expect(() => includes(2, null)).toThrowWithMessage(TypeError, 'Cannot read property \'indexOf\' of null') expect(() => includesRamda(2, null)).toThrowWithMessage(TypeError, 'Cannot read properties of null (reading \'indexOf\')') expect(() => includes(2, undefined)).toThrowWithMessage(TypeError, 'Cannot read property \'indexOf\' of undefined') expect(() => includesRamda(2, undefined)).toThrowWithMessage(TypeError, 'Cannot read properties of undefined (reading \'indexOf\')') })
    Typescript test typescript import {includes} from 'rambda' const list = [{a: {b: '1'}}, {a: {c: '2'}}, {a: {b: '3'}}] describe('R.includes', () => { it('happy', () => { const result = includes({a: {b: '1'}}, list) result // $ExpectType boolean }) it('with string', () => { const result = includes('oo', 'foo') const curriedResult = includes('oo')('foo') result // $ExpectType boolean curriedResult // $ExpectType boolean }) })
    Rambda is faster than Ramda with 84.68% text const R = require('../../dist/rambda.js') const { uniqListOfStrings, uniqListOfBooleans, uniqListOfObjects, uniqListOfLists, listOfVariousTypes, rangeOfNumbers, } = require('./_utils.js') const limit = 100 const additionalModes = listOfVariousTypes.map(unknownType => [ unknownType, uniqListOfLists(limit), ]) const modes = [ [ 99, rangeOfNumbers(limit) ], [ 200, rangeOfNumbers(limit) ], ...additionalModes, [ 'zeppelin', uniqListOfStrings(limit) ], [ null, uniqListOfBooleans(limit) ], [ { foo : true, bar : true, }, uniqListOfObjects(limit) ], [ 1, uniqListOfLists(limit) ], [ [ 1 ], uniqListOfLists(limit) ], ] function applyBenchmark(fn, input){ return fn(input[ 0 ], input[ 1 ]) } const tests = [ { label : 'Rambda', fn : R.includes, }, { label : 'Ramda', fn : Ramda.includes, }, ] tests, modes, applyBenchmark, }

    ---------------

    indexBy

    It generates object with properties provided by condition and values provided by list array.

    If condition is a function, then all list members are passed through it.

    If condition is a string, then all list members are passed through R.path(condition).

    const list = [ {id: 10}, {id: 20} ]
    
    const withFunction = R.indexBy(
      x => x.id,
      list
    )
    const withString = R.indexBy(
      'id',
      list
    )
    const result = [
      withFunction, 
      R.equals(withFunction, withString)
    ]
    // => [ { 10: {id: 10}, 20: {id: 20} }, true ]
    

    Try this R.indexBy example in Rambda REPL

    ---------------

    indexOf

    It returns the index of the first element of list equals to valueToFind.

    If there is no such element, it returns -1.

    :boom: It uses R.equals for list of objects/arrays or native indexOf for any other case.

    const list = [0, 1, 2, 3]
    
    const result = [
      R.indexOf(2, list),
      R.indexOf(0, list)
    ]
    // => [2, -1]
    

    Try this R.indexOf example in Rambda REPL

    ---------------

    init

    
    init<T extends unknown[]>(input: T): T extends readonly [...infer U, any] ? U : [...T]
    

    It returns all but the last element of list or string input.

    const result = [
      R.init([1, 2, 3]) , 
      R.init('foo')  // => 'fo'
    ]
    // => [[1, 2], 'fo']
    

    Try this R.init example in Rambda REPL

    All Typescript definitions typescript init<T extends unknown[]>(input: T): T extends readonly [...infer U, any] ? U : [...T]; init(input: string): string;
    R.init source javascript import baseSlice from './_internals/baseSlice.js' export function init(listOrString){ if (typeof listOrString === 'string') return listOrString.slice(0, -1) return listOrString.length ? baseSlice( listOrString, 0, -1 ) : [] }
    Tests javascript import { init } from './init.js' test('with array', () => { expect(init([ 1, 2, 3 ])).toEqual([ 1, 2 ]) expect(init([ 1, 2 ])).toEqual([ 1 ]) expect(init([ 1 ])).toEqual([]) expect(init([])).toEqual([]) expect(init([])).toEqual([]) expect(init([ 1 ])).toEqual([]) }) test('with string', () => { expect(init('foo')).toEqual('fo') expect(init('f')).toEqual('') expect(init('')).toEqual('') })
    Typescript test typescript import {init} from 'rambda' describe('R.init', () => { it('with string', () => { const result = init('foo') result // $ExpectType string }) it('with list - one type', () => { const result = init([1, 2, 3]) result // $ExpectType number[] }) it('with list - mixed types', () => { const result = init([1, 2, 3, 'foo', 'bar']) result // $ExpectType (string | number)[] }) })
    Rambda is fastest. Ramda is 92.24% slower and Lodash is 13.3% slower text const R = require('../../dist/rambda.js') const list = [ 1, 2, 3, 4 ] const init = [ { label : 'Rambda', fn : () => { R.init(list) }, }, { label : 'Ramda', fn : () => { Ramda.init(list) }, }, { label : 'Lodash', fn : () => { _.initial(list) }, }, ]

    ---------------

    intersection

    It loops throw listA and listB and returns the intersection of the two according to R.equals.

    :boom: There is slight difference between Rambda and Ramda implementation. Ramda.intersection(['a', 'b', 'c'], ['c', 'b']) result is "[ 'c', 'b' ]", but Rambda result is "[ 'b', 'c' ]".

    const listA = [ { id : 1 }, { id : 2 }, { id : 3 }, { id : 4 } ]
    const listB = [ { id : 3 }, { id : 4 }, { id : 5 }, { id : 6 } ]
    
    const result = R.intersection(listA, listB)
    // => [{ id : 3 }, { id : 4 }]
    

    Try this R.intersection example in Rambda REPL

    ---------------

    intersperse

    It adds a separator between members of list.

    const list = [ 0, 1, 2, 3 ]
    const separator = '|'
    const result = intersperse(separator, list)
    // => [0, '|', 1, '|', 2, '|', 3]
    

    Try this R.intersperse example in Rambda REPL

    ---------------

    is

    It returns true if x is instance of targetPrototype.

    const result = [
      R.is(String, 'foo'),  
      R.is(Array, 1)
    ]
    // => [true, false]
    

    Try this R.is example in Rambda REPL

    ---------------

    isEmpty

    
    isEmpty<T>(x: T): boolean
    

    It returns true if x is empty.

    const result = [
      R.isEmpty(''),
      R.isEmpty({ x : 0 })
    ]
    // => [true, false]
    

    Try this R.isEmpty example in Rambda REPL

    All Typescript definitions typescript isEmpty<T>(x: T): boolean;
    R.isEmpty source javascript import { type } from './type.js' export function isEmpty(input){ const inputType = type(input) if ([ 'Undefined', 'NaN', 'Number', 'Null' ].includes(inputType)) return false if (!input) return true if (inputType === 'Object'){ return Object.keys(input).length === 0 } if (inputType === 'Array'){ return input.length === 0 } return false }
    Tests javascript import {isEmpty} from './isEmpty.js' test('happy', () => { expect(isEmpty(undefined)).toBeFalse() expect(isEmpty('')).toBeTrue() expect(isEmpty(null)).toBeFalse() expect(isEmpty(' ')).toBeFalse() expect(isEmpty(new RegExp(''))).toBeFalse() expect(isEmpty([])).toBeTrue() expect(isEmpty([[]])).toBeFalse() expect(isEmpty({})).toBeTrue() expect(isEmpty({x: 0})).toBeFalse() expect(isEmpty(0)).toBeFalse() expect(isEmpty(NaN)).toBeFalse() expect(isEmpty([''])).toBeFalse() })
    Typescript test typescript import {isEmpty} from 'rambda' describe('R.isEmpty', () => { it('happy', () => { const result = isEmpty('foo') result // $ExpectType boolean }) })
    Rambda is fastest. Ramda is 97.14% slower and Lodash is 54.99% slower text const R = require('../../dist/rambda.js') const isEmpty = [ { label : 'Rambda', fn : () => { R.isEmpty(undefined) R.isEmpty('') R.isEmpty(null) R.isEmpty(' ') R.isEmpty(new RegExp('')) R.isEmpty([]) R.isEmpty([ [] ]) R.isEmpty({}) R.isEmpty({ x : 0 }) R.isEmpty(0) R.isEmpty(NaN) R.isEmpty([ '' ]) }, }, { label : 'Ramda', fn : () => { Ramda.isEmpty(undefined) Ramda.isEmpty('') Ramda.isEmpty(null) Ramda.isEmpty(' ') Ramda.isEmpty(new RegExp('')) Ramda.isEmpty([]) Ramda.isEmpty([ [] ]) Ramda.isEmpty({}) Ramda.isEmpty({ x : 0 }) Ramda.isEmpty(0) Ramda.isEmpty(NaN) Ramda.isEmpty([ '' ]) }, }, { label : 'Lodash', fn : () => { _.isEmpty(undefined) _.isEmpty('') _.isEmpty(null) _.isEmpty(' ') _.isEmpty(new RegExp('')) _.isEmpty([]) _.isEmpty([ [] ]) _.isEmpty({}) _.isEmpty({ x : 0 }) _.isEmpty(0) _.isEmpty(NaN) _.isEmpty([ '' ]) }, }, ]

    ---------------

    isNil

    
    isNil(x: any): x is null | undefined
    

    It returns true if x is either null or undefined.

    const result = [
      R.isNil(null),
      R.isNil(1),
    ]
    // => [true, false]
    

    Try this R.isNil example in Rambda REPL

    All Typescript definitions typescript isNil(x: any): x is null | undefined;
    R.isNil source javascript export function isNil(x){ return x === undefined || x === null }
    Tests javascript import { isNil } from './isNil.js' test('happy', () => { expect(isNil(null)).toBeTrue() expect(isNil(undefined)).toBeTrue() expect(isNil([])).toBeFalse() })

    ---------------

    join

    
    join<T>(glue: string, list: T[]): string
    

    It returns a string of all list instances joined with a glue.

    R.join('-', [1, 2, 3])  // => '1-2-3'
    

    Try this R.join example in Rambda REPL

    All Typescript definitions typescript join<T>(glue: string, list: T[]): string; join<T>(glue: string): (list: T[]) => string;
    R.join source javascript export function join(glue, list){ if (arguments.length === 1) return _list => join(glue, _list) return list.join(glue) }
    Tests javascript import { join } from './join.js' test('curry', () => { expect(join('|')([ 'foo', 'bar', 'baz' ])).toEqual('foo|bar|baz') expect(join('|', [ 1, 2, 3 ])).toEqual('1|2|3') const spacer = join(' ') expect(spacer([ 'a', 2, 3.4 ])).toEqual('a 2 3.4') })
    Typescript test typescript import {join} from 'rambda' describe('R.join', () => { it('happy', () => { const result = join('|', [1, 2, 3]) result // $ExpectType string }) })

    ---------------

    juxt

    
    juxt<A extends any[], R1>(fns: [(...a: A) => R1]): (...a: A) => [R1]
    

    It applies list of function to a list of inputs.

    const getRange = juxt([ Math.min, Math.max, Math.min ])
    const result = getRange(
      3, 4, 9, -3
    )
    // => [-3, 9, -3]
    

    Try this R.juxt example in Rambda REPL

    All Typescript definitions typescript juxt<A extends any[], R1>(fns: [(...a: A) => R1]): (...a: A) => [R1]; juxt<A extends any[], R1, R2>(fns: [(...a: A) => R1, (...a: A) => R2]): (...a: A) => [R1, R2]; juxt<A extends any[], R1, R2, R3>(fns: [(...a: A) => R1, (...a: A) => R2, (...a: A) => R3]): (...a: A) => [R1, R2, R3]; juxt<A extends any[], R1, R2, R3, R4>(fns: [(...a: A) => R1, (...a: A) => R2, (...a: A) => R3, (...a: A) => R4]): (...a: A) => [R1, R2, R3, R4]; juxt<A extends any[], R1, R2, R3, R4, R5>(fns: [(...a: A) => R1, (...a: A) => R2, (...a: A) => R3, (...a: A) => R4, (...a: A) => R5]): (...a: A) => [R1, R2, R3, R4, R5]; juxt<A extends any[], U>(fns: Array<(...args: A) => U>): (...args: A) => U[];
    R.juxt source javascript export function juxt(listOfFunctions){ return (...args) => listOfFunctions.map(fn => fn(...args)) }
    Tests javascript import {juxt} from './juxt.js' test('happy', () => { const fn = juxt([Math.min, Math.max, Math.min]) const result = fn(3, 4, 9, -3) expect(result).toEqual([-3, 9, -3]) })
    Typescript test typescript import {juxt} from 'rambda' describe('R.juxt', () => { it('happy', () => { const fn = juxt([Math.min, Math.max]) const result = fn(3, 4, 9, -3) result // $ExpectType [number, number] }) })

    ---------------

    keys

    
    keys<T extends object>(x: T): (keyof T)[]
    

    It applies Object.keys over x and returns its keys.

    R.keys({a:1, b:2})  // => ['a', 'b']
    

    Try this R.keys example in Rambda REPL

    All Typescript definitions typescript keys<T extends object>(x: T): (keyof T)[]; keys<T>(x: T): string[];
    R.keys source javascript export function keys(x){ return Object.keys(x) }
    Tests javascript import { keys } from './keys.js' test('happy', () => { expect(keys({ a : 1 })).toEqual([ 'a' ]) })
    Typescript test typescript import {keys} from 'rambda' const obj = {a: 1, b: 2} describe('R.keys', () => { it('happy', () => { const result = keys(obj) result // $ExpectType ("b" | "a")[] }) })

    ---------------

    last

    
    last(str: string): string
    

    It returns the last element of input, as the input can be either a string or an array.

    const result = [
      R.last([1, 2, 3]),
      R.last('foo'),
    ]
    // => [3, 'o']
    

    Try this R.last example in Rambda REPL

    All Typescript definitions typescript last(str: string): string; last(emptyList: []): undefined; last<T extends any>(list: T[]): T | undefined;
    R.last source javascript export function last(listOrString){ if (typeof listOrString === 'string'){ return listOrString[ listOrString.length - 1 ] || '' } return listOrString[ listOrString.length - 1 ] }
    Tests javascript import { last } from './last.js' test('with list', () => { expect(last([ 1, 2, 3 ])).toBe(3) expect(last([])).toBeUndefined() }) test('with string', () => { expect(last('abc')).toEqual('c') expect(last('')).toEqual('') })
    Typescript test typescript import {last} from 'rambda' describe('R.last', () => { it('string', () => { const result = last('foo') result // $ExpectType string }) it('array', () => { const result = last([1, 2, 3]) result // $ExpectType number | undefined }) it('empty array - case 1', () => { const result = last([]) result // $ExpectType undefined }) it('empty array - case 2', () => { const list = ['foo', 'bar'].filter(x => x.startsWith('a')) const result = last(list) result // $ExpectType string | undefined }) })
    Rambda is fastest. Ramda is 93.43% slower and Lodash is 5.28% slower text const R = require('../../dist/rambda.js') const list = [ 1, 2, 3, 4 ] const last = [ { label : 'Rambda', fn : () => { R.last(list) }, }, { label : 'Ramda', fn : () => { Ramda.last(list) }, }, { label : 'Lodash', fn : () => { _.last(list) }, }, ]

    ---------------

    lastIndexOf

    
    lastIndexOf<T>(target: T, list: T[]): number
    

    It returns the last index of target in list array.

    R.equals is used to determine equality between target and members of list.

    If there is no such index, then -1 is returned.

    const list = [1, 2, 3, 1, 2, 3]
    const result = [
      R.lastIndexOf(2, list),
      R.lastIndexOf(4, list),
    ]
    // => [4, -1]
    

    Try this R.lastIndexOf example in Rambda REPL

    All Typescript definitions typescript lastIndexOf<T>(target: T, list: T[]): number; lastIndexOf<T>(target: T): (list: T[]) => number;
    R.lastIndexOf source javascript import { _lastIndexOf } from './equals.js' export function lastIndexOf(valueToFind, list){ if (arguments.length === 1){ return _list => _lastIndexOf(valueToFind, _list) } return _lastIndexOf(valueToFind, list) }
    Tests javascript import { lastIndexOf as lastIndexOfRamda } from 'ramda' import { compareCombinations } from './_internals/testUtils.js' import { possibleIterables, possibleTargets } from './indexOf.spec.js' import { lastIndexOf } from './lastIndexOf.js' test('with NaN', () => { expect(lastIndexOf(NaN, [ NaN ])).toEqual(0) }) test('will throw with bad input', () => { expect(lastIndexOfRamda([], true)).toEqual(-1) expect(() => indexOf([], true)).toThrow() }) test('without list of objects - no R.equals', () => { expect(lastIndexOf(3, [ 1, 2, 3, 4 ])).toEqual(2) expect(lastIndexOf(10)([ 1, 2, 3, 4 ])).toEqual(-1) }) test('list of objects uses R.equals', () => { const listOfObjects = [ { a : 1 }, { b : 2 }, { c : 3 } ] expect(lastIndexOf({ c : 4 }, listOfObjects)).toBe(-1) expect(lastIndexOf({ c : 3 }, listOfObjects)).toBe(2) }) test('list of arrays uses R.equals', () => { const listOfLists = [ [ 1 ], [ 2, 3 ], [ 2, 3, 4 ], [ 2, 3 ], [ 1 ], [] ] expect(lastIndexOf([], listOfLists)).toBe(5) expect(lastIndexOf([ 1 ], listOfLists)).toBe(4) expect(lastIndexOf([ 2, 3, 4 ], listOfLists)).toBe(2) expect(lastIndexOf([ 2, 3, 5 ], listOfLists)).toBe(-1) }) test('with string as iterable', () => { expect(() => lastIndexOf('a', 'abc')).toThrowWithMessage(Error, 'Cannot read property \'indexOf\' of abc') expect(lastIndexOfRamda('a', 'abc')).toBe(0) }) describe('brute force', () => { compareCombinations({ fn : lastIndexOf, fnRamda : lastIndexOfRamda, firstInput : possibleTargets, secondInput : possibleIterables, callback : errorsCounters => { expect(errorsCounters).toMatchInlineSnapshot(` Object { "ERRORS_MESSAGE_MISMATCH": 0, "ERRORS_TYPE_MISMATCH": 34, "RESULTS_MISMATCH": 0, "SHOULD_NOT_THROW": 51, "SHOULD_THROW": 0, "TOTAL_TESTS": 170, } `) }, }) })
    Typescript test typescript import {lastIndexOf} from 'rambda' const list = [1, 2, 3] describe('R.lastIndexOf', () => { it('happy', () => { const result = lastIndexOf(2, list) result // $ExpectType number }) it('curried', () => { const result = lastIndexOf(2)(list) result // $ExpectType number }) })
    Rambda is faster than Ramda with 85.19% text const R = require('../../dist/rambda.js') const isEven = n => n % 2 === 0 const arr = [ 1, 3, 5, 7, 9, 11 ] const lastIndexOf = [ { label : 'Rambda', fn : () => { R.lastIndexOf(1, [ 1, 2, 3, 1, 2 ]) R.lastIndexOf(1)([ 1, 2, 3, 1, 2 ]) }, }, { label : 'Ramda', fn : () => { Ramda.lastIndexOf(1, [ 1, 2, 3, 1, 2 ]) Ramda.lastIndexOf(1)([ 1, 2, 3, 1, 2 ]) }, }, ]

    ---------------

    length

    
    length<T>(input: T[]): number
    

    It returns the length property of list or string input.

    const result = [
      R.length([1, 2, 3, 4]),
      R.length('foo'),
    ]
    // => [4, 3]
    

    Try this R.length example in Rambda REPL

    All Typescript definitions typescript length<T>(input: T[]): number;
    R.length source javascript import { _isArray } from './_internals/_isArray.js' export function length(x){ if (_isArray(x)) return x.length if (typeof x === 'string') return x.length return NaN }
    Tests javascript import { length as lengthRamda } from 'ramda' import { length } from './length.js' test('happy', () => { expect(length('foo')).toEqual(3) expect(length([ 1, 2, 3 ])).toEqual(3) expect(length([])).toEqual(0) }) test('with empty string', () => { expect(length('')).toEqual(0) }) test('with bad input returns NaN', () => { expect(length(0)).toBeNaN() expect(length({})).toBeNaN() expect(length(null)).toBeNaN() expect(length(undefined)).toBeNaN() }) test('with length as property', () => { const input1 = { length : '123' } const input2 = { length : null } const input3 = { length : '' } expect(length(input1)).toBeNaN() expect(lengthRamda(input1)).toBeNaN() expect(length(input2)).toBeNaN() expect(lengthRamda(input2)).toBeNaN() expect(length(input3)).toBeNaN() expect(lengthRamda(input3)).toBeNaN() })

    ---------------

    lens

    
    lens<T, U, V>(getter: (s: T) => U, setter: (a: U, s: T) => V): Lens
    

    It returns a lens for the given getter and setter functions.

    The getter gets the value of the focus; the setter sets the value of the focus.

    The setter should not mutate the data structure.

    const xLens = R.lens(R.prop('x'), R.assoc('x'));
    
    R.view(xLens, {x: 1, y: 2}) // => 1
    R.set(xLens, 4, {x: 1, y: 2}) // => {x: 4, y: 2}
    R.over(xLens, R.negate, {x: 1, y: 2}) // => {x: -1, y: 2}
    

    Try this R.lens example in Rambda REPL

    All Typescript definitions typescript lens<T, U, V>(getter: (s: T) => U, setter: (a: U, s: T) => V): Lens;
    R.lens source javascript export function lens(getter, setter){ return function (functor){ return function (target){ return functor(getter(target)).map(focus => setter(focus, target)) } } }
    Typescript test typescript import {lens, assoc} from 'rambda' interface Input { foo: string } describe('R.lens', () => { it('happy', () => { const fn = lens<Input, string, string>((x: Input) => { x.foo // $ExpectType string return x.foo }, assoc('name')) fn // $ExpectType Lens }) })

    ---------------

    lensIndex

    
    lensIndex(index: number): Lens
    

    It returns a lens that focuses on specified index.

    const list = ['a', 'b', 'c']
    const headLens = R.lensIndex(0)
    
    R.view(headLens, list) // => 'a'
    R.set(headLens, 'x', list) // => ['x', 'b', 'c']
    R.over(headLens, R.toUpper, list) // => ['A', 'b', 'c']
    

    Try this R.lensIndex example in Rambda REPL

    All Typescript definitions typescript lensIndex(index: number): Lens;
    R.lensIndex source javascript import { lens } from './lens.js' import { nth } from './nth.js' import { update } from './update.js' export function lensIndex(index){ return lens(nth(index), update(index)) }
    Tests javascript import { compose } from './compose.js' import { keys } from './keys.js' import { lensIndex } from './lensIndex.js' import { over } from './over.js' import { set } from './set.js' import { view } from './view.js' const testList = [ { a : 1 }, { b : 2 }, { c : 3 } ] test('focuses list element at the specified index', () => { expect(view(lensIndex(0), testList)).toEqual({ a : 1 }) }) test('returns undefined if the specified index does not exist', () => { expect(view(lensIndex(10), testList)).toEqual(undefined) }) test('sets the list value at the specified index', () => { expect(set( lensIndex(0), 0, testList )).toEqual([ 0, { b : 2 }, { c : 3 } ]) }) test('applies function to the value at the specified list index', () => { expect(over( lensIndex(2), keys, testList )).toEqual([ { a : 1 }, { b : 2 }, [ 'c' ] ]) }) test('can be composed', () => { const nestedList = [ 0, [ 10, 11, 12 ], 1, 2 ] const composedLens = compose(lensIndex(1), lensIndex(0)) expect(view(composedLens, nestedList)).toEqual(10) }) test('set s (get s) === s', () => { expect(set( lensIndex(0), view(lensIndex(0), testList), testList )).toEqual(testList) }) test('get (set s v) === v', () => { expect(view(lensIndex(0), set( lensIndex(0), 0, testList ))).toEqual(0) }) test('get (set(set s v1) v2) === v2', () => { expect(view(lensIndex(0), set( lensIndex(0), 11, set( lensIndex(0), 10, testList ) ))).toEqual(11) })
    Typescript test typescript import {view, lensIndex} from 'rambda' interface Input { a: number } const testList: Input[] = [{a: 1}, {a: 2}, {a: 3}] describe('R.lensIndex', () => { it('happy', () => { const result = view<Input[], Input>(lensIndex(0), testList) result // $ExpectType Input result.a // $ExpectType number }) })

    ---------------

    lensPath

    
    lensPath(path: RamdaPath): Lens
    

    It returns a lens that focuses on specified path.

    const lensPath = R.lensPath(['x', 0, 'y'])
    const input = {x: [{y: 2, z: 3}, {y: 4, z: 5}]}
    
    R.view(lensPath, input) // => 2
    
    R.set(lensPath, 1, input) 
    // => {x: [{y: 1, z: 3}, {y: 4, z: 5}]}
    
    R.over(xHeadYLens, R.negate, input) 
    // => {x: [{y: -2, z: 3}, {y: 4, z: 5}]}
    

    Try this R.lensPath example in Rambda REPL

    All Typescript definitions typescript lensPath(path: RamdaPath): Lens; lensPath(path: string): Lens;
    R.lensPath source javascript import { assocPath } from './assocPath.js' import { lens } from './lens.js' import { path } from './path.js' export function lensPath(key){ return lens(path(key), assocPath(key)) }
    Tests javascript import { compose } from './compose.js' import { identity } from './identity.js' import { inc } from './inc.js' import { lensPath } from './lensPath.js' import { lensProp } from './lensProp.js' import { over } from './over.js' import { set } from './set.js' import { view } from './view.js' const testObj = { a : [ { b : 1 }, { b : 2 } ], d : 3, } test('view', () => { expect(view(lensPath('d'), testObj)).toEqual(3) expect(view(lensPath('a.0.b'), testObj)).toEqual(1) // this is different to ramda, as ramda will return a clone of the input object expect(view(lensPath(''), testObj)).toEqual(undefined) }) test('set', () => { expect(set( lensProp('d'), 0, testObj )).toEqual({ a : [ { b : 1 }, { b : 2 } ], d : 0, }) expect(set( lensPath('a.0.b'), 0, testObj )).toEqual({ a : [ { b : 0 }, { b : 2 } ], d : 3, }) expect(set( lensPath('a.0.X'), 0, testObj )).toEqual({ a : [ { b : 1, X : 0, }, { b : 2 }, ], d : 3, }) expect(set( lensPath([]), 0, testObj )).toEqual(0) }) test('over', () => { expect(over( lensPath('d'), inc, testObj )).toEqual({ a : [ { b : 1 }, { b : 2 } ], d : 4, }) expect(over( lensPath('a.1.b'), inc, testObj )).toEqual({ a : [ { b : 1 }, { b : 3 } ], d : 3, }) expect(over( lensProp('X'), identity, testObj )).toEqual({ a : [ { b : 1 }, { b : 2 } ], d : 3, X : undefined, }) expect(over( lensPath('a.0.X'), identity, testObj )).toEqual({ a : [ { b : 1, X : undefined, }, { b : 2 }, ], d : 3, }) }) test('compose', () => { const composedLens = compose(lensPath('a'), lensPath('1.b')) expect(view(composedLens, testObj)).toEqual(2) }) test('set s (get s) === s', () => { expect(set( lensPath([ 'd' ]), view(lensPath([ 'd' ]), testObj), testObj )).toEqual(testObj) expect(set( lensPath([ 'a', 0, 'b' ]), view(lensPath([ 'a', 0, 'b' ]), testObj), testObj )).toEqual(testObj) }) test('get (set s v) === v', () => { expect(view(lensPath([ 'd' ]), set( lensPath([ 'd' ]), 0, testObj ))).toEqual(0) expect(view(lensPath([ 'a', 0, 'b' ]), set( lensPath([ 'a', 0, 'b' ]), 0, testObj ))).toEqual(0) }) test('get (set(set s v1) v2) === v2', () => { const p = [ 'd' ] const q = [ 'a', 0, 'b' ] expect(view(lensPath(p), set( lensPath(p), 11, set( lensPath(p), 10, testObj ) ))).toEqual(11) expect(view(lensPath(q), set( lensPath(q), 11, set( lensPath(q), 10, testObj ) ))).toEqual(11) })
    Typescript test typescript import {lensPath, view} from 'rambda' interface Input { foo: number[] bar: { a: string b: string } } const testObject: Input = { foo: [1, 2], bar: { a: 'x', b: 'y', }, } const path = lensPath(['bar', 'a']) const pathAsString = lensPath('bar.a') describe('R.lensPath', () => { it('happy', () => { const result = view<Input, string>(path, testObject) result // $ExpectType string }) it('using string as path input', () => { const result = view<Input, string>(pathAsString, testObject) result // $ExpectType string }) })

    ---------------

    lensProp

    
    lensProp(prop: string): {
      <T, U>(obj: T): U
    

    It returns a lens that focuses on specified property prop.

    const xLens = R.lensProp('x');
    const input = {x: 1, y: 2}
    
    R.view(xLens, input) // => 1
    
    R.set(xLens, 4, input) 
    // => {x: 4, y: 2}
    
    R.over(xLens, R.negate, input) 
    // => {x: -1, y: 2}
    

    Try this R.lensProp example in Rambda REPL

    All Typescript definitions typescript lensProp(prop: string): { <T, U>(obj: T): U; set<T, U, V>(val: T, obj: U): V; };
    R.lensProp source javascript import { assoc } from './assoc.js' import { lens } from './lens.js' import { prop } from './prop.js' export function lensProp(key){ return lens(prop(key), assoc(key)) }
    Tests javascript import { compose } from './compose.js' import { identity } from './identity.js' import { inc } from './inc.js' import { lensProp } from './lensProp.js' import { over } from './over.js' import { set } from './set.js' import { view } from './view.js' const testObj = { a : 1, b : 2, c : 3, } test('focuses object the specified object property', () => { expect(view(lensProp('a'), testObj)).toEqual(1) }) test('returns undefined if the specified property does not exist', () => { expect(view(lensProp('X'), testObj)).toEqual(undefined) }) test('sets the value of the object property specified', () => { expect(set( lensProp('a'), 0, testObj )).toEqual({ a : 0, b : 2, c : 3, }) }) test('adds the property to the object if it doesn\'t exist', () => { expect(set( lensProp('d'), 4, testObj )).toEqual({ a : 1, b : 2, c : 3, d : 4, }) }) test('applies function to the value of the specified object property', () => { expect(over( lensProp('a'), inc, testObj )).toEqual({ a : 2, b : 2, c : 3, }) }) test('applies function to undefined and adds the property if it doesn\'t exist', () => { expect(over( lensProp('X'), identity, testObj )).toEqual({ a : 1, b : 2, c : 3, X : undefined, }) }) test('can be composed', () => { const nestedObj = { a : { b : 1 }, c : 2, } const composedLens = compose(lensProp('a'), lensProp('b')) expect(view(composedLens, nestedObj)).toEqual(1) }) test('set s (get s) === s', () => { expect(set( lensProp('a'), view(lensProp('a'), testObj), testObj )).toEqual(testObj) }) test('get (set s v) === v', () => { expect(view(lensProp('a'), set( lensProp('a'), 0, testObj ))).toEqual(0) }) test('get (set(set s v1) v2) === v2', () => { expect(view(lensProp('a'), set( lensProp('a'), 11, set( lensProp('a'), 10, testObj ) ))).toEqual(11) })
    Typescript test typescript import {lensProp, view} from 'rambda' interface Input { foo: string } const testObject: Input = { foo: 'Led Zeppelin', } const lens = lensProp('foo') describe('R.lensProp', () => { it('happy', () => { const result = view<Input, string>(lens, testObject) result // $ExpectType string }) })

    ---------------

    map

    
    map<T, U>(fn: ObjectIterator<T, U>, iterable: Dictionary<T>): Dictionary<U>
    

    It returns the result of looping through iterable with fn.

    It works with both array and object.

    :boom: Unlike Ramda's map, here property and input object are passed as arguments to fn, when iterable is an object.

    const fn = x => x * 2
    const fnWhenObject = (val, prop)=>{
      return `${prop}-${val}`
    }
    
    const iterable = [1, 2]
    const obj = {a: 1, b: 2}
    
    const result = [ 
      R.map(fn, list),
      R.map(fnWhenObject, Record<string, unknown>)
    ]
    // => [ [1, 4], {a: 'a-1', b: 'b-2'}]
    

    Try this R.map example in Rambda REPL

    All Typescript definitions typescript map<T, U>(fn: ObjectIterator<T, U>, iterable: Dictionary<T>): Dictionary<U>; map<T, U>(fn: Iterator<T, U>, iterable: T[]): U[]; map<T, U>(fn: Iterator<T, U>): (iterable: T[]) => U[]; map<T, U, S>(fn: ObjectIterator<T, U>): (iterable: Dictionary<T>) => Dictionary<U>; map<T>(fn: Iterator<T, T>): (iterable: T[]) => T[]; map<T>(fn: Iterator<T, T>, iterable: T[]): T[];
    R.map source javascript import { _isArray } from './_internals/_isArray.js' import { _keys } from './_internals/_keys.js' export function mapArray( fn, list, isIndexed = false ){ let index = 0 const willReturn = Array(list.length) while (index < list.length){ willReturn[ index ] = isIndexed ? fn(list[ index ], index) : fn(list[ index ]) index++ } return willReturn } export function mapObject(fn, obj){ let index = 0 const keys = _keys(obj) const len = keys.length const willReturn = {} while (index < len){ const key = keys[ index ] willReturn[ key ] = fn( obj[ key ], key, obj ) index++ } return willReturn } export const mapObjIndexed = mapObject export function map(fn, iterable){ if (arguments.length === 1) return _iterable => map(fn, _iterable) if (!iterable){ throw new Error('Incorrect iterable input') } if (_isArray(iterable)) return mapArray(fn, iterable) return mapObject(fn, iterable) }
    Tests javascript import { map as mapRamda } from 'ramda' import { map } from './map.js' const double = x => x * 2 describe('with array', () => { it('happy', () => { expect(map(double, [ 1, 2, 3 ])).toEqual([ 2, 4, 6 ]) }) it('curried', () => { expect(map(double)([ 1, 2, 3 ])).toEqual([ 2, 4, 6 ]) }) }) describe('with object', () => { const obj = { a : 1, b : 2, } it('happy', () => { expect(map(double, obj)).toEqual({ a : 2, b : 4, }) }) it('property as second and input object as third argument', () => { const obj = { a : 1, b : 2, } const iterator = ( val, prop, inputObject ) => { expect(prop).toBeString() expect(inputObject).toEqual(obj) return val * 2 } expect(map(iterator)(obj)).toEqual({ a : 2, b : 4, }) }) }) test('bad inputs difference between Ramda and Rambda', () => { expect(() => map(double, null)).toThrowWithMessage(Error, 'Incorrect iterable input') expect(() => map(double)(undefined)).toThrowWithMessage(Error, 'Incorrect iterable input') expect(() => mapRamda(double, null)).toThrowWithMessage(TypeError, 'Cannot read properties of null (reading \'fantasy-land/map\')') expect(() => mapRamda(double, undefined)).toThrowWithMessage(TypeError, 'Cannot read properties of undefined (reading \'fantasy-land/map\')') })
    Typescript test typescript import {map} from 'rambda' describe('R.map with arrays', () => { it('iterable returns the same type as the input', () => { const result = map<number>( (x: number) => { x // $ExpectType number return x + 2 }, [1, 2, 3] ) result // $ExpectType number[] }) it('iterable returns the same type as the input - curried', () => { const result = map<number>((x: number) => { x // $ExpectType number return x + 2 })([1, 2, 3]) result // $ExpectType number[] }) it('iterable returns different type as the input', () => { const result = map<number, string>( (x: number) => { x // $ExpectType number return String(x) }, [1, 2, 3] ) result // $ExpectType string[] }) }) describe('R.map with objects', () => { it('iterable with all three arguments - curried', () => { // It requires dummy third typing argument // in order to identify compared to curry typings for arrays // ============================================ const result = map<number, string, any>((a, b, c) => { a // $ExpectType number b // $ExpectType string c // $ExpectType Dictionary<number> return `${a}` })({a: 1, b: 2}) result // $ExpectType Dictionary<string> }) it('iterable with all three arguments', () => { const result = map<number, string>( (a, b, c) => { a // $ExpectType number b // $ExpectType string c // $ExpectType Dictionary<number> return `${a}` }, {a: 1, b: 2} ) result // $ExpectType Dictionary<string> }) it('iterable with property argument', () => { const result = map<number, string>( (a, b) => { a // $ExpectType number b // $ExpectType string return `${a}` }, {a: 1, b: 2} ) result // $ExpectType Dictionary<string> }) it('iterable with no property argument', () => { const result = map<number, string>( a => { a // $ExpectType number return `${a}` }, {a: 1, b: 2} ) result // $ExpectType Dictionary<string> }) })
    Rambda is fastest. Ramda is 86.6% slower and Lodash is 11.73% slower text const R = require('../../dist/rambda.js') const arr = [ 1, 2, 3, 4 ] const fn = x => x * 2 const map = [ { label : 'Rambda', fn : () => { R.map(fn, arr) }, }, { label : 'Ramda', fn : () => { Ramda.map(fn, arr) }, }, { label : 'Lodash', fn : () => { _.map(arr, fn) }, }, ]

    ---------------

    mapObjIndexed

    It works the same way as R.map does for objects. It is added as Ramda also has this method.

    const fn = (val, prop) => {
      return `${prop}-${val}`
    }
    
    const obj = {a: 1, b: 2}
    
    const result = R.map(mapObjIndexed, Record<string, unknown>)
    // => {a: 'a-1', b: 'b-2'}
    

    Try this R.mapObjIndexed example in Rambda REPL

    ---------------

    match

    
    match(regExpression: RegExp, str: string): string[]
    

    Curried version of String.prototype.match which returns empty array, when there is no match.

    const result = [
      R.match('a', 'foo'),
      R.match(/([a-z]a)/g, 'bananas')
    ]
    // => [[], ['ba', 'na', 'na']]
    

    Try this R.match example in Rambda REPL

    All Typescript definitions typescript match(regExpression: RegExp, str: string): string[]; match(regExpression: RegExp): (str: string) => string[];
    R.match source javascript export function match(pattern, input){ if (arguments.length === 1) return _input => match(pattern, _input) const willReturn = input.match(pattern) return willReturn === null ? [] : willReturn }
    Tests javascript import { equals } from './equals.js' import { match } from './match.js' test('happy', () => { expect(match(/a./g)('foo bar baz')).toEqual([ 'ar', 'az' ]) }) test('fallback', () => { expect(match(/a./g)('foo')).toEqual([]) }) test('with string', () => { expect(match('a', 'foo')).toEqual([]) expect(equals(match('o', 'foo'), [ 'o' ])).toBeTrue() }) test('throwing', () => { expect(() => { match(/a./g, null) }).toThrowWithMessage(TypeError, 'Cannot read properties of null (reading \'match\')') })
    Typescript test typescript import {match} from 'rambda' const str = 'foo bar' describe('R.match', () => { it('happy', () => { const result = match(/foo/, str) result // $ExpectType string[] }) it('curried', () => { const result = match(/foo/)(str) result // $ExpectType string[] }) })
    Rambda is faster than Ramda with 44.83% text const R = require('../../dist/rambda.js') const match = [ { label : 'Rambda', fn : () => { R.match(/a./g)('foo bar baz') R.match(/a./g, 'foo bar baz') }, }, { label : 'Ramda', fn : () => { Ramda.match(/a./g)('foo bar baz') Ramda.match(/a./g, 'foo bar baz') }, }, ]

    ---------------

    mathMod

    R.mathMod behaves like the modulo operator should mathematically, unlike the % operator (and by extension, R.modulo). So while -17 % 5 is -2, mathMod(-17, 5) is 3.

    :boom: Explanation is taken from Ramda documentation site.

    const result = [
      R.mathMod(-17, 5),
      R.mathMod(17, 5),
      R.mathMod(17, -5),  
      R.mathMod(17, 0)   
    ]
    // => [3, 2, NaN, NaN]
    

    Try this R.mathMod example in Rambda REPL

    ---------------

    max

    It returns the greater value between x and y.

    const result = [
      R.max(5, 7),  
      R.max('bar', 'foo'),  
    ]
    // => [7, 'foo']
    

    Try this R.max example in Rambda REPL

    ---------------

    maxBy

    It returns the greater value between x and y according to compareFn function.

    const compareFn = Math.abs
    
    R.maxBy(compareFn, 5, -7) // => -7
    

    Try this R.maxBy example in Rambda REPL

    ---------------

    mean

    
    mean(list: number[]): number
    

    It returns the mean value of list input.

    R.mean([ 2, 7 ])
    // => 4.5
    

    Try this R.mean example in Rambda REPL

    All Typescript definitions typescript mean(list: number[]): number;
    R.mean source javascript import { sum } from './sum.js' export function mean(list){ return sum(list) / list.length }
    Tests javascript import { mean } from './mean.js' test('happy', () => { expect(mean([ 2, 7 ])).toBe(4.5) }) test('with NaN', () => { expect(mean([])).toBeNaN() })
    Typescript test typescript import {mean} from 'rambda' describe('R.mean', () => { it('happy', () => { const result = mean([1, 2, 3]) result // $ExpectType number }) })

    ---------------

    median

    
    median(list: number[]): number
    

    It returns the median value of list input.

    R.median([ 7, 2, 10, 9 ]) // => 8
    

    Try this R.median example in Rambda REPL

    All Typescript definitions typescript median(list: number[]): number;
    R.median source javascript import { mean } from './mean.js' export function median(list){ const len = list.length if (len === 0) return NaN const width = 2 - len % 2 const idx = (len - width) / 2 return mean(Array.prototype.slice .call(list, 0) .sort((a, b) => { if (a === b) return 0 return a < b ? -1 : 1 }) .slice(idx, idx + width)) }
    Tests javascript import { median } from './median.js' test('happy', () => { expect(median([ 2 ])).toEqual(2) expect(median([ 7, 2, 10, 2, 9 ])).toEqual(7) }) test('with empty array', () => { expect(median([])).toBeNaN() })
    Typescript test typescript import {median} from 'rambda' describe('R.median', () => { it('happy', () => { const result = median([1, 2, 3]) result // $ExpectType number }) })

    ---------------

    merge

    Same as R.mergeRight.

    ---------------

    mergeAll

    
    mergeAll<T>(list: object[]): T
    

    It merges all objects of list array sequentially and returns the result.

    const list = [
      {a: 1},
      {b: 2},
      {c: 3}
    ]
    const result = R.mergeAll(list)
    const expected = {
      a: 1,
      b: 2,
      c: 3
    }
    // => `result` is equal to `expected`
    

    Try this R.mergeAll example in Rambda REPL

    All Typescript definitions typescript mergeAll<T>(list: object[]): T; mergeAll(list: object[]): object;
    R.mergeAll source javascript import { map } from './map.js' import { mergeRight } from './mergeRight.js' export function mergeAll(arr){ let willReturn = {} map(val => { willReturn = mergeRight(willReturn, val) }, arr) return willReturn }
    Tests javascript import { mergeAll } from './mergeAll.js' test('case 1', () => { const arr = [ { a : 1 }, { b : 2 }, { c : 3 } ] const expectedResult = { a : 1, b : 2, c : 3, } expect(mergeAll(arr)).toEqual(expectedResult) }) test('case 2', () => { expect(mergeAll([ { foo : 1 }, { bar : 2 }, { baz : 3 } ])).toEqual({ foo : 1, bar : 2, baz : 3, }) })
    Typescript test typescript import {mergeAll} from 'rambda' describe('R.mergeAll', () => { it('with passing type', () => { interface Output { foo: number bar: number } const result = mergeAll<Output>([{foo: 1}, {bar: 2}]) result.foo // $ExpectType number result.bar // $ExpectType number }) it('without passing type', () => { const result = mergeAll([{foo: 1}, {bar: 2}]) result // $ExpectType unknown }) })

    ---------------

    mergeDeepRight

    
    mergeDeepRight<Output>(target: object, newProps: object): Output
    

    Creates a new object with the own properties of the first object merged with the own properties of the second object. If a key exists in both objects:

    • and both values are objects, the two values will be recursively merged
    • otherwise the value from the second object will be used.
    All Typescript definitions typescript mergeDeepRight<Output>(target: object, newProps: object): Output; mergeDeepRight<Output>(target: object): (newProps: object) => Output;
    R.mergeDeepRight source javascript import { type } from './type.js' export function mergeDeepRight(target, source){ if (arguments.length === 1){ return sourceHolder => mergeDeepRight(target, sourceHolder) } const willReturn = JSON.parse(JSON.stringify(target)) Object.keys(source).forEach(key => { if (type(source[ key ]) === 'Object'){ if (type(target[ key ]) === 'Object'){ willReturn[ key ] = mergeDeepRight(target[ key ], source[ key ]) } else { willReturn[ key ] = source[ key ] } } else { willReturn[ key ] = source[ key ] } }) return willReturn }
    Tests javascript import { mergeDeepRight } from './mergeDeepRight.js' const slave = { name : 'evilMe', age : 10, contact : { a : 1, email : 'foo@example.com', }, } const master = { age : 40, contact : { email : 'baz@example.com' }, songs : { title : 'Remains the same' }, } test('happy', () => { const result = mergeDeepRight(slave, master) const curryResult = mergeDeepRight(slave)(master) const expected = { age : 40, name : 'evilMe', contact : { a : 1, email : 'baz@example.com', }, songs : { title : 'Remains the same' }, } expect(result).toEqual(expected) expect(curryResult).toEqual(expected) }) test('ramda compatible test 1', () => { const a = { w : 1, x : 2, y : { z : 3 }, } const b = { a : 4, b : 5, c : { d : 6 }, } const result = mergeDeepRight(a, b) const expected = { w : 1, x : 2, y : { z : 3 }, a : 4, b : 5, c : { d : 6 }, } expect(result).toEqual(expected) }) test('ramda compatible test 2', () => { const a = { a : { b : 1, c : 2, }, y : 0, } const b = { a : { b : 3, d : 4, }, z : 0, } const result = mergeDeepRight(a, b) const expected = { a : { b : 3, c : 2, d : 4, }, y : 0, z : 0, } expect(result).toEqual(expected) }) test('ramda compatible test 3', () => { const a = { w : 1, x : { y : 2 }, } const result = mergeDeepRight(a, { x : { y : 3 } }) const expected = { w : 1, x : { y : 3 }, } expect(result).toEqual(expected) })
    Typescript test typescript import {mergeDeepRight} from 'rambda' interface Output { foo: { bar: number } } describe('R.mergeDeepRight', () => { const result = mergeDeepRight<Output>({foo: {bar: 1}}, {foo: {bar: 2}}) result.foo.bar // $ExpectType number })

    ---------------

    mergeLeft

    
    mergeLeft<Output>(newProps: object, target: object): Output
    

    Same as R.merge, but in opposite direction.

    const result = R.mergeLeft(
      {a: 10},
      {a: 1, b: 2}
    )
    // => {a:10, b: 2}
    

    Try this R.mergeLeft example in Rambda REPL

    All Typescript definitions typescript mergeLeft<Output>(newProps: object, target: object): Output; mergeLeft<Output>(newProps: object): (target: object) => Output;
    R.mergeLeft source javascript import { mergeRight } from './mergeRight.js' export function mergeLeft(x, y){ if (arguments.length === 1) return _y => mergeLeft(x, _y) return mergeRight(y, x) }
    Tests javascript import { mergeLeft } from './mergeLeft.js' const obj = { foo : 1, bar : 2, } test('happy', () => { expect(mergeLeft({ bar : 20 }, obj)).toEqual({ foo : 1, bar : 20, }) }) test('curry', () => { expect(mergeLeft({ baz : 3 })(obj)).toEqual({ foo : 1, bar : 2, baz : 3, }) }) test('when undefined or null instead of object', () => { expect(mergeLeft(null, undefined)).toEqual({}) expect(mergeLeft(obj, null)).toEqual(obj) expect(mergeLeft(obj, undefined)).toEqual(obj) expect(mergeLeft(undefined, obj)).toEqual(obj) })
    Typescript test typescript import {mergeLeft} from 'rambda' interface Output { foo: number bar: number } describe('R.mergeLeft', () => { const result = mergeLeft<Output>({foo: 1}, {bar: 2}) const curriedResult = mergeLeft<Output>({foo: 1})({bar: 2}) result.foo // $ExpectType number result.bar // $ExpectType number curriedResult.bar // $ExpectType number })

    ---------------

    mergeRight

    It creates a copy of target object with overidden newProps properties. Previously known as R.merge but renamed after Ramda did the same.

    const target = { 'foo': 0, 'bar': 1 }
    const newProps = { 'foo': 7 }
    
    const result = R.mergeRight(target, newProps)
    // => { 'foo': 7, 'bar': 1 }
    

    Try this R.mergeRight example in Rambda REPL

    ---------------

    mergeWith

    
    mergeWith(fn: (x: any, z: any) => any, a: Record<string, unknown>, b: Record<string, unknown>): Record<string, unknown>
    

    It takes two objects and a function, which will be used when there is an overlap between the keys.

    const result = R.mergeWith(
      R.concat,
      {values : [ 10, 20 ]},
      {values : [ 15, 35 ]}
    )
    // => [ 10, 20, 15, 35 ]
    

    Try this R.mergeWith example in Rambda REPL

    All Typescript definitions typescript mergeWith(fn: (x: any, z: any) => any, a: Record<string, unknown>, b: Record<string, unknown>): Record<string, unknown>; mergeWith<Output>(fn: (x: any, z: any) => any, a: Record<string, unknown>, b: Record<string, unknown>): Output; mergeWith(fn: (x: any, z: any) => any, a: Record<string, unknown>): (b: Record<string, unknown>) => Record<string, unknown>; mergeWith<Output>(fn: (x: any, z: any) => any, a: Record<string, unknown>): (b: Record<string, unknown>) => Output; mergeWith(fn: (x: any, z: any) => any): <U, V>(a: U, b: V) => Record<string, unknown>; mergeWith<Output>(fn: (x: any, z: any) => any): <U, V>(a: U, b: V) => Output;
    R.mergeWith source javascript import { curry } from './curry.js' function mergeWithFn( mergeFn, a, b ){ const willReturn = {} Object.keys(a).forEach(key => { if (b[ key ] === undefined){ willReturn[ key ] = a[ key ] } else { willReturn[ key ] = mergeFn(a[ key ], b[ key ]) } }) Object.keys(b).forEach(key => { if (willReturn[ key ] !== undefined) return if (a[ key ] === undefined){ willReturn[ key ] = b[ key ] } else { willReturn[ key ] = mergeFn(a[ key ], b[ key ]) } }) return willReturn } export const mergeWith = curry(mergeWithFn)
    Tests javascript import { concat } from './concat.js' import { mergeWith } from './mergeWith.js' test('happy', () => { const result = mergeWith( concat, { a : true, values : [ 10, 20 ], }, { b : true, values : [ 15, 35 ], } ) const expected = { a : true, values : [ 10, 20, 15, 35 ], b : true, } expect(result).toEqual(expected) })
    Typescript test typescript import {concat, mergeWith} from 'rambda' interface Output { a: boolean, b: boolean, values: number[], } const A = { a: true, values: [10, 20], } const B = { b: true, values: [15, 35], } describe('R.mergeWith', () => { test('no curry | without explicit types', () => { const result = mergeWith(concat, A, B) result // $ExpectType Obj }) test('no curry | with explicit types', () => { const result = mergeWith<Output>(concat, A, B) result // $ExpectType Output }) test('curry 1 | without explicit types', () => { const result = mergeWith(concat, A)(B) result // $ExpectType Obj }) test('curry 1 | with explicit types', () => { const result = mergeWith<Output>(concat, A)(B) result // $ExpectType Output }) test('curry 2 | without explicit types', () => { const result = mergeWith(concat)(A, B) result // $ExpectType Obj }) test('curry 2 | with explicit types', () => { const result = mergeWith<Output>(concat)(A, B) result // $ExpectType Output }) })

    ---------------

    min

    It returns the lesser value between x and y.

    const result = [
      R.min(5, 7),  
      R.min('bar', 'foo'),  
    ]
    // => [5, 'bar']
    

    Try this R.min example in Rambda REPL

    ---------------

    minBy

    It returns the lesser value between x and y according to compareFn function.

    const compareFn = Math.abs
    
    R.minBy(compareFn, -5, 2) // => -5
    

    Try this R.minBy example in Rambda REPL

    ---------------

    modulo

    Curried version of x%y.

    R.modulo(17, 3) // => 2
    

    Try this R.modulo example in Rambda REPL

    ---------------

    move

    It returns a copy of list with exchanged fromIndex and toIndex elements.

    :boom: Rambda.move doesn't support negative indexes - it throws an error.

    const list = [1, 2, 3]
    const result = R.move(0, 1, list)
    // => [2, 1, 3]
    

    Try this R.move example in Rambda REPL

    ---------------

    multiply

    Curried version of x*y.

    R.multiply(2, 4) // => 8
    

    Try this R.multiply example in Rambda REPL

    ---------------

    negate

    R.negate(420)// => -420
    

    Try this R.negate example in Rambda REPL

    ---------------

    none

    
    none<T>(predicate: (x: T) => boolean, list: T[]): boolean
    

    It returns true, if all members of array list returns false, when applied as argument to predicate function.

    const list = [ 0, 1, 2, 3, 4 ]
    const predicate = x => x > 6
    
    const result = R.none(predicate, arr)
    // => true
    

    Try this R.none example in Rambda REPL

    All Typescript definitions typescript none<T>(predicate: (x: T) => boolean, list: T[]): boolean; none<T>(predicate: (x: T) => boolean): (list: T[]) => boolean;
    R.none source javascript export function none(predicate, list){ if (arguments.length === 1) return _list => none(predicate, _list) for (let i = 0; i < list.length; i++){ if (predicate(list[ i ])) return false } return true }
    Tests javascript import {none} from './none.js' const isEven = n => n % 2 === 0 test('when true', () => { expect(none(isEven, [1, 3, 5, 7])).toBeTrue() }) test('when false curried', () => { expect(none(input => input > 1, [1, 2, 3])).toBeFalse() })
    Typescript test typescript import {none} from 'rambda' describe('R.none', () => { it('happy', () => { const result = none( x => { x // $ExpectType number return x > 0 }, [1, 2, 3] ) result // $ExpectType boolean }) it('curried needs a type', () => { const result = none<number>(x => { x // $ExpectType number return x > 0 })([1, 2, 3]) result // $ExpectType boolean }) })
    Rambda is faster than Ramda with 96.48% text const R = require('../../dist/rambda.js') const isEven = n => n % 2 === 0 const arr = [ 1, 3, 5, 7, 9, 11 ] const none = [ { label : 'Rambda', fn : () => { R.none(isEven, arr) R.none(isEven)(arr) }, }, { label : 'Ramda', fn : () => { Ramda.none(isEven, arr) Ramda.none(isEven)(arr) }, }, ]

    ---------------

    not

    
    not(input: any): boolean
    

    It returns a boolean negated version of input.

    R.not(false) // true
    

    Try this R.not example in Rambda REPL

    All Typescript definitions typescript not(input: any): boolean;
    R.not source javascript export function not(input){ return !input }
    Tests javascript import {not} from './not.js' test('not', () => { expect(not(false)).toBeTrue() expect(not(true)).toBeFalse() expect(not(0)).toBeTrue() expect(not(1)).toBeFalse() })
    Typescript test typescript import {not} from 'rambda' describe('R.not', () => { it('happy', () => { const result = not(4) result // $ExpectType boolean }) })

    ---------------

    nth

    
    nth(index: number, input: string): string
    

    Curried version of input[index].

    const list = [1, 2, 3]
    const str = 'foo'
    
    const result = [
      R.nth(2, list),
      R.nth(6, list),
      R.nth(0, str),
    ]
    // => [3, undefined, 'f']
    

    Try this R.nth example in Rambda REPL

    All Typescript definitions typescript nth(index: number, input: string): string; nth<T>(index: number, input: T[]): T | undefined; nth(n: number): { <T>(input: T[]): T | undefined; (input: string): string; };
    R.nth source javascript export function nth(index, input){ if (arguments.length === 1) return _input => nth(index, _input) const idx = index < 0 ? input.length + index : index return Object.prototype.toString.call(input) === '[object String]' ? input.charAt(idx) : input[ idx ] }
    Tests javascript import { nth } from './nth.js' test('happy', () => { expect(nth(2, [ 1, 2, 3, 4 ])).toEqual(3) }) test('with curry', () => { expect(nth(2)([ 1, 2, 3, 4 ])).toEqual(3) }) test('with string and correct index', () => { expect(nth(2)('foo')).toEqual('o') }) test('with string and invalid index', () => { expect(nth(20)('foo')).toEqual('') }) test('with negative index', () => { expect(nth(-3)([ 1, 2, 3, 4 ])).toEqual(2) })
    Typescript test typescript import {nth} from 'rambda' const list = [1, 2, 3] describe('R.nth', () => { it('happy', () => { const result = nth(4, list) result // $ExpectType number | undefined }) it('curried', () => { const result = nth(1)(list) result // $ExpectType number | undefined }) }) describe('R.nth - string', () => { const str = 'abc' it('happy', () => { const result = nth(4, str) result // $ExpectType string }) it('curried', () => { const result = nth(1)(str) result // $ExpectType string }) })

    ---------------

    objOf

    It creates an object with a single key-value pair.

    const result = R.objOf('foo', 'bar')
    // => {foo: 'bar'}
    

    Try this R.objOf example in Rambda REPL

    ---------------

    of

    
    of<T>(x: T): T[]
    
    R.of(null); // => [null]
    R.of([42]); // => [[42]]
    

    Try this R.of example in Rambda REPL

    All Typescript definitions typescript of<T>(x: T): T[];
    R.of source javascript export function of(value){ return [ value ] }
    Tests javascript import { of } from './of.js' test('happy', () => { expect(of(3)).toEqual([ 3 ]) expect(of(null)).toEqual([ null ]) })
    Typescript test typescript import {of} from 'ramda' const list = [1, 2, 3] describe('R.of', () => { it('happy', () => { const result = of(4) result // $ExpectType number[] }) it('curried', () => { const result = of(list) result // $ExpectType number[][] }) })

    ---------------

    omit

    
    omit<T, K extends string>(propsToOmit: K[], obj: T): Omit<T, K>
    

    It returns a partial copy of an obj without propsToOmit properties.

    :boom: When using this method with TypeScript, it is much easier to pass propsToOmit as an array. If passing a string, you will need to explicitly declare the output type.

    const obj = {a: 1, b: 2, c: 3}
    const propsToOmit = 'a,c,d'
    const propsToOmitList = ['a', 'c', 'd']
    
    const result = [
      R.omit(propsToOmit, Record<string, unknown>), 
      R.omit(propsToOmitList, Record<string, unknown>) 
    ]
    // => [{b: 2}, {b: 2}]
    

    Try this R.omit example in Rambda REPL

    All Typescript definitions typescript omit<T, K extends string>(propsToOmit: K[], obj: T): Omit<T, K>; omit<K extends string>(propsToOmit: K[]): <T>(obj: T) => Omit<T, K>; omit<T, U>(propsToOmit: string, obj: T): U; omit<T, U>(propsToOmit: string): (obj: T) => U; omit<T>(propsToOmit: string, obj: object): T; omit<T>(propsToOmit: string): (obj: object) => T;
    R.omit source javascript import { createPath } from './_internals/createPath.js' export function omit(propsToOmit, obj){ if (arguments.length === 1) return _obj => omit(propsToOmit, _obj) if (obj === null || obj === undefined){ return undefined } const propsToOmitValue = createPath(propsToOmit, ',') const willReturn = {} for (const key in obj){ if (!propsToOmitValue.includes(key)){ willReturn[ key ] = obj[ key ] } } return willReturn }
    Tests javascript import { omit } from './omit.js' test('with string as condition', () => { const obj = { a : 1, b : 2, c : 3, } const result = omit('a,c', obj) const resultCurry = omit('a,c')(obj) const expectedResult = { b : 2 } expect(result).toEqual(expectedResult) expect(resultCurry).toEqual(expectedResult) }) test('with null', () => { expect(omit('a,b', null)).toEqual(undefined) }) test('doesn\'t work with number as property', () => { expect(omit([ 42 ], { a : 1, 42 : 2, })).toEqual({ 42 : 2, a : 1, }) }) test('happy', () => { expect(omit([ 'a', 'c' ])({ a : 'foo', b : 'bar', c : 'baz', })).toEqual({ b : 'bar' }) })
    Typescript test typescript import {omit} from 'rambda' describe('R.omit with array as props input', () => { it('allow Typescript to infer object type', () => { const input = {a: 'foo', b: 2, c: 3, d: 4} const result = omit(['b,c'], input) result.a // $ExpectType string result.d // $ExpectType number const curriedResult = omit(['a,c'], input) curriedResult.a // $ExpectType string curriedResult.d // $ExpectType number }) it('declare type of input object', () => { interface Input { a: string b: number c: number d: number } const input: Input = {a: 'foo', b: 2, c: 3, d: 4} const result = omit(['b,c'], input) result // $ExpectType Omit<Input, "b,c"> result.a // $ExpectType string result.d // $ExpectType number const curriedResult = omit(['a,c'], input) curriedResult.a // $ExpectType string curriedResult.d // $ExpectType number }) }) describe('R.omit with string as props input', () => { interface Output { b: number d: number } it('explicitly declare output', () => { const result = omit<Output>('a,c', {a: 1, b: 2, c: 3, d: 4}) result // $ExpectType Output result.b // $ExpectType number const curriedResult = omit<Output>('a,c')({a: 1, b: 2, c: 3, d: 4}) curriedResult.b // $ExpectType number }) it('explicitly declare input and output', () => { interface Input { a: number b: number c: number d: number } const result = omit<Input, Output>('a,c', {a: 1, b: 2, c: 3, d: 4}) result // $ExpectType Output result.b // $ExpectType number const curriedResult = omit<Input, Output>('a,c')({ a: 1, b: 2, c: 3, d: 4, }) curriedResult.b // $ExpectType number }) it('without passing type', () => { const result = omit('a,c', {a: 1, b: 2, c: 3, d: 4}) result // $ExpectType unknown }) })
    Rambda is fastest. Ramda is 69.95% slower and Lodash is 97.34% slower text const R = require('../../dist/rambda.js') const obj = { a : 'foo', b : 'bar', c : 'baz', } const toOmit = [ 'a', 'c' ] const omit = [ { label : 'Rambda', fn : () => { R.omit(toOmit, obj) }, }, { label : 'Ramda', fn : () => { Ramda.omit(toOmit, obj) }, }, { label : 'Lodash', fn : () => { _.omit(obj, toOmit) }, }, ]

    ---------------

    on

    It passes the two inputs through unaryFn and then the results are passed as inputs the the binaryFn to receive the final result(binaryFn(unaryFn(FIRST_INPUT), unaryFn(SECOND_INPUT))).

    This method is also known as P combinator.

    const result = R.on((a, b) => a + b, R.prop('a'), {b:0, a:1}, {a:2})
    // => 3
    

    Try this R.on example in Rambda REPL

    ---------------

    once

    
    once<T extends (...args: any[]) => any>(func: T): T
    

    It returns a function, which invokes only once fn function.

    let result = 0
    const addOnce = R.once((x) => result = result + x)
    
    addOnce(1)
    addOnce(1)
    // => 1
    

    Try this R.once example in Rambda REPL

    All Typescript definitions typescript once<T extends (...args: any[]) => any>(func: T): T;
    R.once source javascript import { curry } from './curry.js' function onceFn(fn, context){ let result return function (){ if (fn){ result = fn.apply(context || this, arguments) fn = null } return result } } export function once(fn, context){ if (arguments.length === 1){ const wrap = onceFn(fn, context) return curry(wrap) } return onceFn(fn, context) }
    Tests javascript import { once } from './once.js' test('with counter', () => { let counter = 0 const runOnce = once(x => { counter++ return x + 2 }) expect(runOnce(1)).toEqual(3) runOnce(1) runOnce(1) runOnce(1) expect(counter).toEqual(1) }) test('happy path', () => { const addOneOnce = once(( a, b, c ) => a + b + c, 1) expect(addOneOnce( 10, 20, 30 )).toBe(60) expect(addOneOnce(40)).toEqual(60) })
    Typescript test typescript import {once} from 'rambda' describe('R.once', () => { it('happy', () => { const runOnce = once((x: number) => { return x + 2 }) const result = runOnce(1) result // $ExpectType number }) })

    ---------------

    or

    Logical OR

    R.or(false, true); // => true
    R.or(false, false); // => false
    R.or(false, 'foo'); // => 'foo'
    

    Try this R.or example in Rambda REPL

    ---------------

    over

    
    over<T>(lens: Lens, fn: Arity1Fn, value: T): T
    

    It returns a copied Object or Array with modified value received by applying function fn to lens focus.

    const headLens = R.lensIndex(0)
    
    R.over(headLens, R.toUpper, ['foo', 'bar', 'baz']) // => ['FOO', 'bar', 'baz']
    

    Try this R.over example in Rambda REPL

    All Typescript definitions typescript over<T>(lens: Lens, fn: Arity1Fn, value: T): T; over<T>(lens: Lens, fn: Arity1Fn, value: T[]): T[]; over(lens: Lens, fn: Arity1Fn): <T>(value: T) => T; over(lens: Lens, fn: Arity1Fn): <T>(value: T[]) => T[]; over(lens: Lens): <T>(fn: Arity1Fn, value: T) => T; over(lens: Lens): <T>(fn: Arity1Fn, value: T[]) => T[];
    R.over source javascript import { curry } from './curry.js' const Identity = x => ({ x, map : fn => Identity(fn(x)), }) function overFn( lens, fn, object ){ return lens(x => Identity(fn(x)))(object).x } export const over = curry(overFn)
    Tests javascript import { assoc } from './assoc.js' import { lens } from './lens.js' import { lensIndex } from './lensIndex.js' import { lensPath } from './lensPath.js' import { over } from './over.js' import { prop } from './prop.js' import { toUpper } from './toUpper.js' const testObject = { foo : 'bar', baz : { a : 'x', b : 'y', }, } test('assoc lens', () => { const assocLens = lens(prop('foo'), assoc('foo')) const result = over( assocLens, toUpper, testObject ) const expected = { ...testObject, foo : 'BAR', } expect(result).toEqual(expected) }) test('path lens', () => { const pathLens = lensPath('baz.a') const result = over( pathLens, toUpper, testObject ) const expected = { ...testObject, baz : { a : 'X', b : 'y', }, } expect(result).toEqual(expected) }) test('index lens', () => { const indexLens = lensIndex(0) const result = over(indexLens, toUpper)([ 'foo', 'bar' ]) expect(result).toEqual([ 'FOO', 'bar' ]) })
    Rambda is faster than Ramda with 56.23% text const R = require('../../dist/rambda.js') const testObj = { a : 1 } const last = [ { label : 'Rambda', fn : () => { R.over( R.lensProp('a'), R.inc, testObj ) }, }, { label : 'Ramda', fn : () => { Ramda.over( Ramda.lensProp('a'), Ramda.inc, testObj ) }, }, ]

    ---------------

    partial

    
    partial<V0, V1, T>(fn: (x0: V0, x1: V1) => T, args: [V0]): (x1: V1) => T
    

    It is very similar to R.curry, but you can pass initial arguments when you create the curried function.

    R.partial will keep returning a function until all the arguments that the function fn expects are passed. The name comes from the fact that you partially inject the inputs.

    :boom: Rambda's partial doesn't need the input arguments to be wrapped as array.

    const fn = (title, firstName, lastName) => {
      return title + ' ' + firstName + ' ' + lastName + '!'
    }
    
    const canPassAnyNumberOfArguments = R.partial(fn, 'Hello')
    const ramdaStyle = R.partial(fn, ['Hello'])
    
    const finalFn = canPassAnyNumberOfArguments('Foo')
    
    finalFn('Bar') // =>  'Hello, Foo Bar!'
    

    Try this R.partial example in Rambda REPL

    All Typescript definitions typescript partial<V0, V1, T>(fn: (x0: V0, x1: V1) => T, args: [V0]): (x1: V1) => T; partial<V0, V1, V2, T>(fn: (x0: V0, x1: V1, x2: V2) => T, args: [V0, V1]): (x2: V2) => T; partial<V0, V1, V2, T>(fn: (x0: V0, x1: V1, x2: V2) => T, args: [V0]): (x1: V1, x2: V2) => T; partial<V0, V1, V2, V3, T>(fn: (x0: V0, x1: V1, x2: V2, x3: V3) => T, args: [V0, V1, V2]): (x2: V3) => T; partial<V0, V1, V2, V3, T>(fn: (x0: V0, x1: V1, x2: V2, x3: V3) => T, args: [V0, V1]): (x2: V2, x3: V3) => T; partial<V0, V1, V2, V3, T>(fn: (x0: V0, x1: V1, x2: V2, x3: V3) => T, args: [V0]): (x1: V1, x2: V2, x3: V3) => T; partial<T>(fn: (...a: any[]) => T, args: any[]): (...x: any[]) => T;
    R.partial source javascript export function partial(fn, ...args){ const len = fn.length return (...rest) => { if (args.length + rest.length >= len){ return fn(...args, ...rest) } return partial(fn, ...[ ...args, ...rest ]) } }
    Tests javascript import { partial } from './partial.js' import { type } from './type.js' const greet = ( salutation, title, firstName, lastName ) => salutation + ', ' + title + ' ' + firstName + ' ' + lastName + '!' test('happy', () => { const canPassAnyNumberOfArguments = partial( greet, 'Hello', 'Ms.' ) const fn = canPassAnyNumberOfArguments('foo') const sayHello = partial(greet, [ 'Hello' ]) const sayHelloRamda = partial(sayHello, [ 'Ms.' ]) expect(type(fn)).toBe('Function') expect(fn('bar')).toBe('Hello, Ms. foo bar!') expect(sayHelloRamda('foo', 'bar')).toBe('Hello, Ms. foo bar!') }) test('extra arguments are ignored', () => { const canPassAnyNumberOfArguments = partial( greet, 'Hello', 'Ms.' ) const fn = canPassAnyNumberOfArguments('foo') expect(type(fn)).toBe('Function') expect(fn( 'bar', 1, 2 )).toBe('Hello, Ms. foo bar!') }) test('when array is input', () => { const fooFn = ( a, b, c, d ) => ({ a, b, c, d, }) const barFn = partial( fooFn, [ 1, 2 ], [] ) expect(barFn(1, 2)).toEqual({ a : [ 1, 2 ], b : [], c : 1, d : 2, }) }) test('ramda spec', () => { const sayHello = partial(greet, 'Hello') const sayHelloToMs = partial(sayHello, 'Ms.') expect(sayHelloToMs('Jane', 'Jones')).toBe('Hello, Ms. Jane Jones!') })
    Typescript test typescript import {partial} from 'rambda' describe('R.partial', () => { it('happy', () => { function greet( salutation: string, title: string, firstName: string, lastName: string ) { return `${salutation}, ${title} ${firstName} ${lastName}!` } const sayHello = partial(greet, ['Hello']) const sayHelloToMs = partial(sayHello, ['Ms.']) const result = sayHelloToMs('Jane', 'Jones') result // $ExpectType string }) })

    ---------------

    partialObject

    
    partialObject<Input, PartialInput, Output>(
      fn: (input: Input) => Output, 
      partialInput: PartialInput,
    ): (input: Pick<Input, Exclude<keyof Input, keyof PartialInput>>) => Output
    

    R.partialObject is a curry helper designed specifically for functions accepting object as a single argument.

    Initially the function knows only a part from the whole input object and then R.partialObject helps in preparing the function for the second part, when it receives the rest of the input.

    :boom: Function input can be asynchronous

    const fn = ({ a, b, c }) => a + b + c
    const curried = R.partialObject(fn, { a : 1 })
    const result = curried({
      b : 2,
      c : 3,
    })
    // => 6
    

    Try this R.partialObject example in Rambda REPL

    All Typescript definitions typescript partialObject<Input, PartialInput, Output>( fn: (input: Input) => Output, partialInput: PartialInput, ): (input: Pick<Input, Exclude<keyof Input, keyof PartialInput>>) => Output;
    R.partialObject source javascript import { mergeDeepRight } from './mergeDeepRight.js' import { type } from './type.js' export function partialObject(fn, input){ return rest => { if (type(fn) === 'Async'){ return new Promise((resolve, reject) => { fn(mergeDeepRight(rest, input)).then(resolve) .catch(reject) }) } return fn(mergeDeepRight(rest, input)) } }
    Tests javascript import {delay} from './delay.js' import {partialObject} from './partialObject.js' import {type} from './type.js' test('with plain function', () => { const fn = ({a, b, c}) => a + b + c const curried = partialObject(fn, {a: 1}) expect(type(curried)).toEqual('Function') expect( curried({ b: 2, c: 3, }) ).toEqual(6) }) test('with function that throws an error', () => { const fn = ({a, b, c}) => { throw new Error('foo') } const curried = partialObject(fn, {a: 1}) expect(type(curried)).toEqual('Function') expect(() => curried({ b: 2, c: 3, }) ).toThrowWithMessage(Error, 'foo') }) test('with async', async () => { const fn = async ({a, b, c}) => { await delay(100) return a + b + c } const curried = partialObject(fn, {a: 1}) const result = await curried({ b: 2, c: 3, }) expect(result).toEqual(6) }) test('async function throwing an error', async () => { const fn = async ({a, b, c}) => { await delay(100) throw new Error('foo') } const curried = partialObject(fn, {a: 1}) try { await curried({ b: 2, c: 3, }) expect(true).toBeFalsy() } catch (e) { expect(e.message).toBe('foo') } })
    Typescript test typescript import {partialObject, delay} from 'rambda' describe('R.partialObject', () => { it('happy', () => { interface Input { a: number, b: number, c: string, } const fn = ({a, b, c}: Input) => a + b + c const curried = partialObject(fn, {a: 1}) const result = curried({ b: 2, c: 'foo', }) result // $ExpectType string }) it('asynchronous', async() => { interface Input { a: number, b: number, c: string, } const fn = async({a, b, c}: Input) => { await delay(100) return a + b + c } const curried = partialObject(fn, {a: 1}) const result = await curried({ b: 2, c: 'foo', }) result // $ExpectType string }) })

    ---------------

    partition

    
    partition<T>(
      predicate: Predicate<T>,
      input: T[]
    ): [T[], T[]]
    

    It will return array of two objects/arrays according to predicate function. The first member holds all instances of input that pass the predicate function, while the second member - those who doesn't.

    const list = [1, 2, 3]
    const obj = {a: 1, b: 2, c: 3}
    const predicate = x => x > 2
    
    const result = [
      R.partition(predicate, list),
      R.partition(predicate, Record<string, unknown>)
    ]
    const expected = [
      [[3], [1, 2]],
      [{c: 3},  {a: 1, b: 2}],
    ]
    // `result` is equal to `expected`
    

    Try this R.partition example in Rambda REPL

    All Typescript definitions typescript partition<T>( predicate: Predicate<T>, input: T[] ): [T[], T[]]; partition<T>( predicate: Predicate<T> ): (input: T[]) => [T[], T[]]; partition<T>( predicate: (x: T, prop?: string) => boolean, input: { [key: string]: T} ): [{ [key: string]: T}, { [key: string]: T}]; partition<T>( predicate: (x: T, prop?: string) => boolean ): (input: { [key: string]: T}) => [{ [key: string]: T}, { [key: string]: T}];
    R.partition source javascript import { _isArray } from './_internals/_isArray.js' export function partitionObject(predicate, iterable){ const yes = {} const no = {} Object.entries(iterable).forEach(([ prop, value ]) => { if (predicate(value, prop)){ yes[ prop ] = value } else { no[ prop ] = value } }) return [ yes, no ] } export function partitionArray( predicate, list, indexed = false ){ const yes = [] const no = [] let counter = -1 while (counter++ < list.length - 1){ if ( indexed ? predicate(list[ counter ], counter) : predicate(list[ counter ]) ){ yes.push(list[ counter ]) } else { no.push(list[ counter ]) } } return [ yes, no ] } export function partition(predicate, iterable){ if (arguments.length === 1){ return listHolder => partition(predicate, listHolder) } if (!_isArray(iterable)) return partitionObject(predicate, iterable) return partitionArray(predicate, iterable) }
    Tests javascript import { partition } from './partition.js' test('with array', () => { const predicate = x => x > 2 const list = [ 1, 2, 3, 4 ] const result = partition(predicate, list) const expectedResult = [ [ 3, 4 ], [ 1, 2 ], ] expect(result).toEqual(expectedResult) }) test('with object', () => { const predicate = (value, prop) => { expect(typeof prop).toBe('string') return value > 2 } const hash = { a : 1, b : 2, c : 3, d : 4, } const result = partition(predicate)(hash) const expectedResult = [ { c : 3, d : 4, }, { a : 1, b : 2, }, ] expect(result).toEqual(expectedResult) }) test('readme example', () => { const list = [ 1, 2, 3 ] const obj = { a : 1, b : 2, c : 3, } const predicate = x => x > 2 const result = [ partition(predicate, list), partition(predicate, obj) ] const expected = [ [ [ 3 ], [ 1, 2 ] ], [ { c : 3 }, { a : 1, b : 2, }, ], ] expect(result).toEqual(expected) })
    Typescript test typescript import {partition} from 'rambda' describe('R.partition', () => { it('with array', () => { const predicate = (x: number) => { return x > 2 } const list = [1, 2, 3, 4] const result = partition(predicate, list) const curriedResult = partition(predicate)(list) result // $ExpectType [number[], number[]] curriedResult // $ExpectType [number[], number[]] }) /* TODO revert to old version of `dtslint` and `R.partition` typing as there is diff between VSCode types(correct) and dtslint(incorrect) it('with object', () => { const predicate = (value: number, prop?: string) => { return value > 2 } const hash = { a: 1, b: 2, c: 3, d: 4, } const result = partition(predicate, hash) const curriedResult = partition(predicate)(hash) result[0] // $xExpectType { [key: string]: number; } result[1] // $xExpectType { [key: string]: number; } curriedResult[0] // $xExpectType { [key: string]: number; } curriedResult[1] // $xExpectType { [key: string]: number; } }) */ })

    ---------------

    path

    
    path<Input, T>(pathToSearch: Path, obj: Input): T | undefined
    

    If pathToSearch is 'a.b' then it will return 1 if obj is {a:{b:1}}.

    It will return undefined, if such path is not found.

    :boom: String anotation of pathToSearch is one of the differences between Rambda and Ramda.

    const obj = {a: {b: 1}}
    const pathToSearch = 'a.b'
    const pathToSearchList = ['a', 'b']
    
    const result = [
      R.path(pathToSearch, Record<string, unknown>),
      R.path(pathToSearchList, Record<string, unknown>),
      R.path('a.b.c.d', Record<string, unknown>)
    ]
    // => [1, 1, undefined]
    

    Try this R.path example in Rambda REPL

    All Typescript definitions typescript path<Input, T>(pathToSearch: Path, obj: Input): T | undefined; path<T>(pathToSearch: Path, obj: any): T | undefined; path<T>(pathToSearch: Path): (obj: any) => T | undefined; path<Input, T>(pathToSearch: Path): (obj: Input) => T | undefined;
    R.path source javascript import { createPath } from './_internals/createPath.js' export function path(pathInput, obj){ if (arguments.length === 1) return _obj => path(pathInput, _obj) if (obj === null || obj === undefined){ return undefined } let willReturn = obj let counter = 0 const pathArrValue = createPath(pathInput) while (counter < pathArrValue.length){ if (willReturn === null || willReturn === undefined){ return undefined } if (willReturn[ pathArrValue[ counter ] ] === null) return undefined willReturn = willReturn[ pathArrValue[ counter ] ] counter++ } return willReturn }
    Tests javascript import { path } from './path.js' test('with array inside object', () => { const obj = { a : { b : [ 1, { c : 1 } ] } } expect(path('a.b.1.c', obj)).toBe(1) }) test('works with undefined', () => { const obj = { a : { b : { c : 1 } } } expect(path('a.b.c.d.f', obj)).toBeUndefined() expect(path('foo.babaz', undefined)).toBeUndefined() expect(path('foo.babaz')(undefined)).toBeUndefined() }) test('works with string instead of array', () => { expect(path('foo.bar.baz')({ foo : { bar : { baz : 'yes' } } })).toEqual('yes') }) test('path', () => { expect(path([ 'foo', 'bar', 'baz' ])({ foo : { bar : { baz : 'yes' } } })).toEqual('yes') expect(path([ 'foo', 'bar', 'baz' ])(null)).toBeUndefined() expect(path([ 'foo', 'bar', 'baz' ])({ foo : { bar : 'baz' } })).toBeUndefined() }) test('null is not a valid path', () => { expect(path('audio_tracks', { a : 1, audio_tracks : null, })).toBeUndefined() })
    Typescript test typescript import {path} from 'rambda' interface Input { a: number b: { c: boolean } } describe('R.path', () => { it('without specified input type', () => { const input = {a: 1, b: {c: true}} const result = path<boolean>('a.b.c', input) const curriedResult = path<boolean>('a.b.c')(input) result // $ExpectType boolean | undefined curriedResult // $ExpectType boolean | undefined }) it('without specified output type', () => { const input = {a: 1, b: {c: true}} const result = path('a.b.c', input) result // $ExpectType unknown }) it('with string as path', () => { const input: Input = {a: 1, b: {c: true}} const resultA = path<boolean>('a.b.c', input) const resultB = path<boolean>('a.b.c')(input) resultA // $ExpectType boolean | undefined resultB // $ExpectType boolean | undefined }) it('with array as path', () => { const input: Input = {a: 1, b: {c: true}} const resultA = path<boolean>(['a', 'b', 'c'], input) const resultB = path<boolean>(['a', 'b', 'c'])(input) resultA // $ExpectType boolean | undefined resultB // $ExpectType boolean | undefined }) }) describe('path with specified input', () => { it('with string as path', () => { const input: Input = {a: 1, b: {c: true}} // const wrongInput = { a: 1, b: true } // const resultA = path<Input, boolean>('a.b.c', wrongInput) const resultA = path<Input, boolean>('a.b.c', input) const resultB = path<Input, boolean>('a.b.c')(input) resultA // $ExpectType boolean | undefined resultB // $ExpectType boolean | undefined }) it('with array as path', () => { const input: Input = {a: 1, b: {c: true}} const resultA = path<Input, boolean>(['a', 'b', 'c'], input) const resultB = path<Input, boolean>(['a', 'b', 'c'])(input) resultA // $ExpectType boolean | undefined resultB // $ExpectType boolean | undefined }) })
    Lodash is fastest. Rambda is 37.81% slower and Ramda is 77.81% slower text const R = require('../../dist/rambda.js') const obj = { a : { b : 2 } } const pathInput = [ 'a', 'b' ] const path = [ { label : 'Rambda', fn : () => { R.path(pathInput, obj) }, }, { label : 'Ramda', fn : () => { Ramda.path(pathInput, obj) }, }, { label : 'Lodash', fn : () => { _.get(obj, pathInput) }, }, ]

    ---------------

    pathEq

    
    pathEq(pathToSearch: Path, target: any, input: any): boolean
    

    It returns true if pathToSearch of input object is equal to target value.

    pathToSearch is passed to R.path, which means that it can be either a string or an array. Also equality between target and the found value is determined by R.equals.

    const path = 'a.b'
    const target = {c: 1}
    const input = {a: {b: {c: 1}}}
    
    const result = R.pathEq(
      path,
      target,
      input
    )
    // => true
    

    Try this R.pathEq example in Rambda REPL

    All Typescript definitions typescript pathEq(pathToSearch: Path, target: any, input: any): boolean; pathEq(pathToSearch: Path, target: any): (input: any) => boolean; pathEq(pathToSearch: Path): (target: any) => (input: any) => boolean;
    R.pathEq source javascript import { curry } from './curry.js' import { equals } from './equals.js' import { path } from './path.js' function pathEqFn( pathToSearch, target, input ){ return equals(path(pathToSearch, input), target) } export const pathEq = curry(pathEqFn)
    Tests javascript import { pathEq } from './pathEq.js' test('when true', () => { const path = 'a.b' const obj = { a : { b : { c : 1 } } } const target = { c : 1 } expect(pathEq( path, target, obj )).toBeTrue() }) test('when false', () => { const path = 'a.b' const obj = { a : { b : 1 } } const target = 2 expect(pathEq(path, target)(obj)).toBeFalse() }) test('when wrong path', () => { const path = 'foo.bar' const obj = { a : { b : 1 } } const target = 2 expect(pathEq( path, target, obj )).toBeFalse() })
    Typescript test typescript import {pathEq} from 'rambda' describe('R.pathEq', () => { it('with string path', () => { const pathToSearch = 'a.b.c' const input = {a: {b: {c: 1}}} const target = {c: 1} const result = pathEq(pathToSearch, input, target) const curriedResult = pathEq(pathToSearch, input, target) result // $ExpectType boolean curriedResult // $ExpectType boolean }) it('with array path', () => { const pathToSearch = ['a', 'b', 'c'] const input = {a: {b: {c: 1}}} const target = {c: 1} const result = pathEq(pathToSearch, input, target) const curriedResult = pathEq(pathToSearch, input, target) result // $ExpectType boolean curriedResult // $ExpectType boolean }) }) describe('with ramda specs', () => { const testPath = ['x', 0, 'y'] const testObj = { x: [ {y: 2, z: 3}, {y: 4, z: 5}, ], } const result1 = pathEq(testPath, 2, testObj) const result2 = pathEq(testPath, 2)(testObj) const result3 = pathEq(testPath)(2)(testObj) result1 // $ExpectType boolean result2 // $ExpectType boolean result3 // $ExpectType boolean })

    ---------------

    pathOr

    
    pathOr<T>(defaultValue: T, pathToSearch: Path, obj: any): T
    

    It reads obj input and returns either R.path(pathToSearch, Record<string, unknown>) result or defaultValue input.

    const defaultValue = 'DEFAULT_VALUE'
    const pathToSearch = 'a.b'
    const pathToSearchList = ['a', 'b']
    
    const obj = {
      a : {
        b : 1
      }
    }
    
    const result = [
      R.pathOr(DEFAULT_VALUE, pathToSearch, Record<string, unknown>),
      R.pathOr(DEFAULT_VALUE, pathToSearchList, Record<string, unknown>), 
      R.pathOr(DEFAULT_VALUE, 'a.b.c', Record<string, unknown>)
    ]
    // => [1, 1, 'DEFAULT_VALUE']
    

    Try this R.pathOr example in Rambda REPL

    All Typescript definitions typescript pathOr<T>(defaultValue: T, pathToSearch: Path, obj: any): T; pathOr<T>(defaultValue: T, pathToSearch: Path): (obj: any) => T; pathOr<T>(defaultValue: T): (pathToSearch: Path) => (obj: any) => T;
    R.pathOr source javascript import { curry } from './curry.js' import { defaultTo } from './defaultTo.js' import { path } from './path.js' function pathOrFn( defaultValue, pathInput, obj ){ return defaultTo(defaultValue, path(pathInput, obj)) } export const pathOr = curry(pathOrFn)
    Tests javascript import { pathOr } from './pathOr.js' test('with undefined', () => { const result = pathOr( 'foo', 'x.y', { x : { y : 1 } } ) expect(result).toEqual(1) }) test('with null', () => { const result = pathOr( 'foo', 'x.y', null ) expect(result).toEqual('foo') }) test('with NaN', () => { const result = pathOr( 'foo', 'x.y', NaN ) expect(result).toEqual('foo') }) test('curry case (x)(y)(z)', () => { const result = pathOr('foo')('x.y.z')({ x : { y : { a : 1 } } }) expect(result).toEqual('foo') }) test('curry case (x)(y,z)', () => { const result = pathOr('foo', 'x.y.z')({ x : { y : { a : 1 } } }) expect(result).toEqual('foo') }) test('curry case (x,y)(z)', () => { const result = pathOr('foo')('x.y.z', { x : { y : { a : 1 } } }) expect(result).toEqual('foo') })
    Typescript test typescript import {pathOr} from 'rambda' describe('R.pathOr', () => { it('with string path', () => { const x = pathOr<string>('foo', 'x.y', {x: {y: 'bar'}}) x // $ExpectType string }) it('with array path', () => { const x = pathOr<string>('foo', ['x', 'y'], {x: {y: 'bar'}}) x // $ExpectType string }) it('without passing type looks bad', () => { const x = pathOr('foo', 'x.y', {x: {y: 'bar'}}) x // $ExpectType "foo" }) it('curried', () => { const x = pathOr<string>('foo', 'x.y')({x: {y: 'bar'}}) x // $ExpectType string }) })

    ---------------

    paths

    
    paths<Input, T>(pathsToSearch: Path[], obj: Input): (T | undefined)[]
    

    It loops over members of pathsToSearch as singlePath and returns the array produced by R.path(singlePath, Record<string, unknown>).

    Because it calls R.path, then singlePath can be either string or a list.

    const obj = {
      a : {
        b : {
          c : 1,
          d : 2
        }
      }
    }
    
    const result = R.paths([
      'a.b.c',
      'a.b.d',
      'a.b.c.d.e',
    ], Record<string, unknown>)
    // => [1, 2, undefined]
    

    Try this R.paths example in Rambda REPL

    All Typescript definitions typescript paths<Input, T>(pathsToSearch: Path[], obj: Input): (T | undefined)[]; paths<Input, T>(pathsToSearch: Path[]): (obj: Input) => (T | undefined)[]; paths<T>(pathsToSearch: Path[], obj: any): (T | undefined)[]; paths<T>(pathsToSearch: Path[]): (obj: any) => (T | undefined)[];
    R.paths source javascript import { path } from './path.js' export function paths(pathsToSearch, obj){ if (arguments.length === 1){ return _obj => paths(pathsToSearch, _obj) } return pathsToSearch.map(singlePath => path(singlePath, obj)) }
    Tests javascript import { paths } from './paths.js' const obj = { a : { b : { c : 1, d : 2, }, }, p : [ { q : 3 } ], x : { y : 'FOO', z : [ [ {} ] ], }, } test('with string path + curry', () => { const pathsInput = [ 'a.b.d', 'p.q' ] const expected = [ 2, undefined ] const result = paths(pathsInput, obj) const curriedResult = paths(pathsInput)(obj) expect(result).toEqual(expected) expect(curriedResult).toEqual(expected) }) test('with array path', () => { const result = paths([ [ 'a', 'b', 'c' ], [ 'x', 'y' ], ], obj) expect(result).toEqual([ 1, 'FOO' ]) }) test('takes a paths that contains indices into arrays', () => { expect(paths([ [ 'p', 0, 'q' ], [ 'x', 'z', 0, 0 ], ], obj)).toEqual([ 3, {} ]) expect(paths([ [ 'p', 0, 'q' ], [ 'x', 'z', 2, 1 ], ], obj)).toEqual([ 3, undefined ]) }) test('gets a deep property\'s value from objects', () => { expect(paths([ [ 'a', 'b' ] ], obj)).toEqual([ obj.a.b ]) expect(paths([ [ 'p', 0 ] ], obj)).toEqual([ obj.p[ 0 ] ]) }) test('returns undefined for items not found', () => { expect(paths([ [ 'a', 'x', 'y' ] ], obj)).toEqual([ undefined ]) expect(paths([ [ 'p', 2 ] ], obj)).toEqual([ undefined ]) })
    Typescript test typescript import {paths} from 'rambda' interface Input { a: number b: number c: number } const input: Input = {a: 1, b: 2, c: 3} describe('R.paths', () => { it('with dot notation', () => { const result = paths<number>(['a.b.c', 'foo.bar'], input) result // $ExpectType (number | undefined)[] }) it('without type', () => { const result = paths(['a.b.c', 'foo.bar'], input) result // $ExpectType unknown[] }) it('with array as path', () => { const result = paths<number>([['a', 'b', 'c'], ['foo.bar']], input) result // $ExpectType (number | undefined)[] }) it('curried', () => { const result = paths<number>([['a', 'b', 'c'], ['foo.bar']])(input) result // $ExpectType (number | undefined)[] }) })

    ---------------

    pick

    
    pick<T, K extends string | number | symbol>(propsToPick: K[], input: T): Pick<T, Exclude<keyof T, Exclude<keyof T, K>>>
    

    It returns a partial copy of an input containing only propsToPick properties.

    input can be either an object or an array.

    String anotation of propsToPick is one of the differences between Rambda and Ramda.

    :boom: When using this method with TypeScript, it is much easier to pass propsToPick as an array. If passing a string, you will need to explicitly declare the output type.

    const obj = {
      a : 1,
      b : false,
      foo: 'cherry'
    }
    const list = [1, 2, 3, 4]
    const propsToPick = 'a,foo'
    const propsToPickList = ['a', 'foo']
    
    const result = [
      R.pick(propsToPick, Record<string, unknown>),
      R.pick(propsToPickList, Record<string, unknown>),
      R.pick('a,bar', Record<string, unknown>),
      R.pick('bar', Record<string, unknown>),
      R.pick([0, 3, 5], list),
      R.pick('0,3,5', list),
    ]
    
    const expected = [
      {a:1, foo: 'cherry'},
      {a:1, foo: 'cherry'},
      {a:1},
      {},
      {0: 1, 3: 4},
      {0: 1, 3: 4},
    ]
    // => `result` is equal to `expected`
    

    Try this R.pick example in Rambda REPL

    All Typescript definitions typescript pick<T, K extends string | number | symbol>(propsToPick: K[], input: T): Pick<T, Exclude<keyof T, Exclude<keyof T, K>>>; pick<K extends string | number | symbol>(propsToPick: K[]): <T>(input: T) => Pick<T, Exclude<keyof T, Exclude<keyof T, K>>>; pick<T, U>(propsToPick: string, input: T): U; pick<T, U>(propsToPick: string): (input: T) => U; pick<T>(propsToPick: string, input: object): T; pick<T>(propsToPick: string): (input: object) => T;
    R.pick source javascript import { createPath } from './_internals/createPath.js' export function pick(propsToPick, input){ if (arguments.length === 1) return _input => pick(propsToPick, _input) if (input === null || input === undefined){ return undefined } const keys = createPath(propsToPick, ',') const willReturn = {} let counter = 0 while (counter < keys.length){ if (keys[ counter ] in input){ willReturn[ keys[ counter ] ] = input[ keys[ counter ] ] } counter++ } return willReturn }
    Tests javascript import { pick } from './pick.js' const obj = { a : 1, b : 2, c : 3, } test('props to pick is a string', () => { const result = pick('a,c', obj) const resultCurry = pick('a,c')(obj) const expectedResult = { a : 1, c : 3, } expect(result).toEqual(expectedResult) expect(resultCurry).toEqual(expectedResult) }) test('when prop is missing', () => { const result = pick('a,d,f', obj) expect(result).toEqual({ a : 1 }) }) test('with list indexes as props', () => { const list = [ 1, 2, 3 ] const expected = { 0 : 1, 2 : 3, } expect(pick([ 0, 2, 3 ], list)).toEqual(expected) expect(pick('0,2,3', list)).toEqual(expected) }) test('props to pick is an array', () => { expect(pick([ 'a', 'c' ])({ a : 'foo', b : 'bar', c : 'baz', })).toEqual({ a : 'foo', c : 'baz', }) expect(pick([ 'a', 'd', 'e', 'f' ])({ a : 'foo', b : 'bar', c : 'baz', })).toEqual({ a : 'foo' }) expect(pick('a,d,e,f')(null)).toEqual(undefined) }) test('works with list as input and number as props - props to pick is an array', () => { const result = pick([ 1, 2 ], [ 'a', 'b', 'c', 'd' ]) expect(result).toEqual({ 1 : 'b', 2 : 'c', }) }) test('works with list as input and number as props - props to pick is a string', () => { const result = pick('1,2', [ 'a', 'b', 'c', 'd' ]) expect(result).toEqual({ 1 : 'b', 2 : 'c', }) }) test('with symbol', () => { const symbolProp = Symbol('s') expect(pick([ symbolProp ], { [ symbolProp ] : 'a' })).toMatchInlineSnapshot(` Object { Symbol(s): "a", } `) })
    Typescript test typescript import {pick} from 'rambda' const input = {a: 'foo', b: 2, c: 3, d: 4} describe('R.pick with array as props input', () => { it('without passing type', () => { const result = pick(['a', 'c'], input) result.a // $ExpectType string result.c // $ExpectType number }) }) describe('R.pick with string as props input', () => { interface Input { a: string b: number c: number d: number } interface Output { a: string c: number } it('explicitly declare output', () => { const result = pick<Output>('a,c', input) result // $ExpectType Output result.a // $ExpectType string result.c // $ExpectType number const curriedResult = pick<Output>('a,c')(input) curriedResult.a // $ExpectType string }) it('explicitly declare input and output', () => { const result = pick<Input, Output>('a,c', input) result // $ExpectType Output result.a // $ExpectType string const curriedResult = pick<Input, Output>('a,c')(input) curriedResult.a // $ExpectType string }) it('without passing type', () => { const result = pick('a,c', input) result // $ExpectType unknown }) })
    Rambda is fastest. Ramda is 19.07% slower and Lodash is 80.2% slower text const R = require('../../dist/rambda.js') const obj = { a : 'foo', b : 'bar', c : 'baz', } const pickInput = [ 'a', 'c' ] const pick = [ { label : 'Rambda', fn : () => { R.pick(pickInput, obj) }, }, { label : 'Ramda', fn : () => { Ramda.pick(pickInput, obj) }, }, { label : 'Lodash', fn : () => { _.pick(obj, pickInput) }, }, ]

    ---------------

    pickAll

    
    pickAll<T, U>(propsToPick: string[], input: T): U
    

    Same as R.pick but it won't skip the missing props, i.e. it will assign them to undefined.

    :boom: When using this method with TypeScript, it is much easier to pass propsToPick as an array. If passing a string, you will need to explicitly declare the output type.

    const obj = {
      a : 1,
      b : false,
      foo: 'cherry'
    }
    const propsToPick = 'a,foo,bar'
    const propsToPickList = ['a', 'foo', 'bar']
    
    const result = [
      R.pickAll(propsToPick, Record<string, unknown>),
      R.pickAll(propsToPickList, Record<string, unknown>),
      R.pickAll('a,bar', Record<string, unknown>),
      R.pickAll('bar', Record<string, unknown>),
    ]
    const expected = [
      {a:1, foo: 'cherry', bar: undefined},
      {a:1, foo: 'cherry', bar: undefined},
      {a:1, bar: undefined},
      {bar: undefined}
    ]
    // => `result` is equal to `expected`
    

    Try this R.pickAll example in Rambda REPL

    All Typescript definitions typescript pickAll<T, U>(propsToPick: string[], input: T): U; pickAll<T, U>(propsToPick: string[]): (input: T) => U; pickAll<T, U>(propsToPick: string, input: T): U; pickAll<T, U>(propsToPick: string): (input: T) => U;
    R.pickAll source javascript import { createPath } from './_internals/createPath.js' export function pickAll(propsToPick, obj){ if (arguments.length === 1) return _obj => pickAll(propsToPick, _obj) if (obj === null || obj === undefined){ return undefined } const keysValue = createPath(propsToPick, ',') const willReturn = {} let counter = 0 while (counter < keysValue.length){ if (keysValue[ counter ] in obj){ willReturn[ keysValue[ counter ] ] = obj[ keysValue[ counter ] ] } else { willReturn[ keysValue[ counter ] ] = undefined } counter++ } return willReturn }
    Tests javascript import { pickAll } from './pickAll.js' test('when input is undefined or null', () => { expect(pickAll('a', null)).toBe(undefined) expect(pickAll('a', undefined)).toBe(undefined) }) test('with string as condition', () => { const obj = { a : 1, b : 2, c : 3, } const result = pickAll('a,c', obj) const resultCurry = pickAll('a,c')(obj) const expectedResult = { a : 1, b : undefined, c : 3, } expect(result).toEqual(expectedResult) expect(resultCurry).toEqual(expectedResult) }) test('with array as condition', () => { expect(pickAll([ 'a', 'b', 'c' ], { a : 'foo', c : 'baz', })).toEqual({ a : 'foo', b : undefined, c : 'baz', }) })
    Typescript test typescript import {pickAll} from 'rambda' interface Input { a: string b: number c: number d: number } interface Output { a?: string c?: number } const input = {a: 'foo', b: 2, c: 3, d: 4} describe('R.pickAll with array as props input', () => { it('without passing type', () => { const result = pickAll(['a', 'c'], input) result // $ExpectType unknown }) it('without passing type + curry', () => { const result = pickAll(['a', 'c'])(input) result // $ExpectType unknown }) it('explicitly passing types', () => { const result = pickAll<Input, Output>(['a', 'c'], input) result.a // $ExpectType string | undefined result.c // $ExpectType number | undefined }) it('explicitly passing types + curry', () => { const result = pickAll<Input, Output>(['a', 'c'])(input) result.a // $ExpectType string | undefined result.c // $ExpectType number | undefined }) }) describe('R.pickAll with string as props input', () => { it('without passing type', () => { const result = pickAll('a,c', input) result // $ExpectType unknown }) it('without passing type + curry', () => { const result = pickAll('a,c')(input) result // $ExpectType unknown }) it('explicitly passing types', () => { const result = pickAll<Input, Output>('a,c', input) result.a // $ExpectType string | undefined result.c // $ExpectType number | undefined }) it('explicitly passing types + curry', () => { const result = pickAll<Input, Output>('a,c')(input) result.a // $ExpectType string | undefined result.c // $ExpectType number | undefined }) })

    ---------------

    pipe

    It performs left-to-right function composition.

    const result = R.pipe(
      R.filter(val => val > 2),
      R.map(a => a * 2)
    )([1, 2, 3, 4])
    
    // => [6, 8]
    

    Try this R.pipe example in Rambda REPL

    ---------------

    pluck

    
    pluck<K extends keyof T, T>(property: K, list: T[]): T[K][]
    

    It returns list of the values of property taken from the all objects inside list.

    const list = [{a: 1}, {a: 2}, {b: 3}]
    const property = 'a'
    
    const result = R.pluck(property, list) 
    // => [1, 2]
    

    Try this R.pluck example in Rambda REPL

    All Typescript definitions typescript pluck<K extends keyof T, T>(property: K, list: T[]): T[K][]; pluck<T>(property: number, list: { [k: number]: T }[]): T[]; pluck<P extends string>(property: P): <T>(list: Record<P, T>[]) => T[]; pluck(property: number): <T>(list: { [k: number]: T }[]) => T[];
    R.pluck source javascript import { map } from './map.js' export function pluck(property, list){ if (arguments.length === 1) return _list => pluck(property, _list) const willReturn = [] map(x => { if (x[ property ] !== undefined){ willReturn.push(x[ property ]) } }, list) return willReturn }
    Tests javascript import { pluck } from './pluck.js' test('happy', () => { expect(pluck('a')([ { a : 1 }, { a : 2 }, { b : 1 } ])).toEqual([ 1, 2 ]) }) test('with number', () => { const input = [ [ 1, 2 ], [ 3, 4 ], ] expect(pluck(0, input)).toEqual([ 1, 3 ]) })
    Typescript test typescript import {pluck} from 'rambda' describe('R.pluck', () => { it('with object', () => { interface ListMember { a: number b: string } const input: ListMember[] = [ {a: 1, b: 'foo'}, {a: 2, b: 'bar'}, ] const resultA = pluck('a', input) const resultB = pluck('b')(input) resultA // $ExpectType number[] resultB // $ExpectType string[] }) it('with array', () => { const input = [ [1, 2], [3, 4], [5, 6], ] const result = pluck(0, input) const resultCurry = pluck(0)(input) result // $ExpectType number[] resultCurry // $ExpectType number[] }) })

    ---------------

    prepend

    
    prepend<T>(x: T, input: T[]): T[]
    

    It adds element x at the beginning of list.

    const result = R.prepend('foo', ['bar', 'baz'])
    // => ['foo', 'bar', 'baz']
    

    Try this R.prepend example in Rambda REPL

    All Typescript definitions typescript prepend<T>(x: T, input: T[]): T[]; prepend<T>(x: T): (input: T[]) => T[];
    R.prepend source javascript export function prepend(x, input){ if (arguments.length === 1) return _input => prepend(x, _input) if (typeof input === 'string') return [ x ].concat(input.split('')) return [ x ].concat(input) }
    Tests javascript import { prepend } from './prepend.js' test('happy', () => { expect(prepend('yes', [ 'foo', 'bar', 'baz' ])).toEqual([ 'yes', 'foo', 'bar', 'baz', ]) }) test('with empty list', () => { expect(prepend('foo')([])).toEqual([ 'foo' ]) }) test('with string instead of array', () => { expect(prepend('foo')('bar')).toEqual([ 'foo', 'b', 'a', 'r' ]) })
    Typescript test typescript import {prepend} from 'rambda' const list = [1, 2, 3] describe('R.prepend', () => { it('happy', () => { const result = prepend(4, list) result // $ExpectType number[] }) it('curried', () => { const result = prepend(4)(list) result // $ExpectType number[] }) })

    ---------------

    product

    
    product(list: number[]): number
    
    R.product([ 2, 3, 4 ])
    // => 24)
    

    Try this R.product example in Rambda REPL

    All Typescript definitions typescript product(list: number[]): number;
    R.product source javascript import { multiply } from './multiply.js' import { reduce } from './reduce.js' export const product = reduce(multiply, 1)
    Tests javascript import { product } from './product.js' test('happy', () => { expect(product([ 2, 3, 4 ])).toEqual(24) }) test('bad input', () => { expect(product([ null ])).toEqual(0) expect(product([])).toEqual(1) })
    Typescript test typescript import {product} from 'rambda' describe('R.product', () => { it('happy', () => { const result = product([1, 2, 3]) result // $ExpectType number }) })

    ---------------

    prop

    
    prop<P extends keyof O, O>(propToFind: P, obj: O): O[P]
    

    It returns the value of property propToFind in obj.

    If there is no such property, it returns undefined.

    const result = [
      R.prop('x', {x: 100}), 
      R.prop('x', {a: 1}) 
    ]
    // => [100, undefined]
    

    Try this R.prop example in Rambda REPL

    All Typescript definitions typescript prop<P extends keyof O, O>(propToFind: P, obj: O): O[P]; prop<P extends keyof O, O>(propToFind: P): (obj: O) => O[P]; prop<P extends string | number>(propToFind: P): <T>(obj: Record<P, T>) => T; prop<P extends string | number, T>(propToFind: P): (obj: Record<P, T>) => T;
    R.prop source javascript export function prop(propToFind, obj){ if (arguments.length === 1) return _obj => prop(propToFind, _obj) if (!obj) return undefined return obj[ propToFind ] }
    Tests javascript import { prop } from './prop.js' test('prop', () => { expect(prop('foo')({ foo : 'baz' })).toEqual('baz') expect(prop('bar')({ foo : 'baz' })).toEqual(undefined) expect(prop('bar')(null)).toEqual(undefined) })
    Typescript test typescript import {pipe, prop} from 'rambda' describe('R.prop', () => { const obj = {a: 1, b: 'foo'} type Something = {a?: number, b?: string} it('issue #553', () => { const result = prop('e', {e: 'test1', d: 'test2'}) const curriedResult = prop<string>('e')({e: 'test1', d: 'test2'}) result // $ExpectType string curriedResult // $ExpectType string }) it('happy', () => { const result = prop('a', obj) result // $ExpectType number }) it('curried', () => { const result = prop('b')(obj) result // $ExpectType string }) it('curried with explicit object type', () => { const result = prop<'a', Something>('a')(obj) result // $ExpectType number | undefined }) it('curried with implicit object type', () => { const result = pipe((value) => value as Something, prop('b'))(obj) result // $ExpectType string | undefined }) it('curried with explicit result type', () => { const result = prop<'b', string>('b')(obj) result // $ExpectType string }) }) describe('with number as prop', () => { const list = [1, 2, 3] const index = 1 it('happy', () => { const result = prop(index, list) result // $ExpectType number }) it('curried require explicit type', () => { const result = prop<number>(index)(list) result // $ExpectType number }) })
    Rambda is faster than Ramda with 87.95% text const R = require('../../dist/rambda.js') const obj = { a : { c : 2 }, b : 1, } const propInput = 'b' const prop = [ { label : 'Rambda', fn : () => { R.prop(propInput, obj) R.prop(propInput)(obj) }, }, { label : 'Ramda', fn : () => { Ramda.prop(propInput, obj) Ramda.prop(propInput)(obj) }, }, ]

    ---------------

    propEq

    
    propEq<K extends string | number>(propToFind: K, valueToMatch: any, obj: Record<K, any>): boolean
    

    It returns true if obj has property propToFind and its value is equal to valueToMatch.

    const obj = { foo: 'bar' }
    const secondObj = { foo: 1 }
    
    const propToFind = 'foo'
    const valueToMatch = 'bar'
    
    const result = [
      R.propEq(propToFind, valueToMatch, Record<string, unknown>),
      R.propEq(propToFind, valueToMatch, secondRecord<string, unknown>)
    ]
    // => [true, false]
    

    Try this R.propEq example in Rambda REPL

    All Typescript definitions typescript propEq<K extends string | number>(propToFind: K, valueToMatch: any, obj: Record<K, any>): boolean; propEq<K extends string | number>(propToFind: K, valueToMatch: any): (obj: Record<K, any>) => boolean; propEq<K extends string | number>(propToFind: K): { (valueToMatch: any, obj: Record<K, any>): boolean; (valueToMatch: any): (obj: Record<K, any>) => boolean; };
    R.propEq source javascript import { curry } from './curry.js' function propEqFn( propToFind, valueToMatch, obj ){ if (!obj) return false return obj[ propToFind ] === valueToMatch } export const propEq = curry(propEqFn)
    Tests javascript import { propEq } from './propEq.js' test('happy', () => { expect(propEq('foo', 'bar')({ foo : 'bar' })).toBeTrue() expect(propEq('foo', 'bar')({ foo : 'baz' })).toBeFalse() expect(propEq('foo')('bar')({ foo : 'baz' })).toBeFalse() expect(propEq( 'foo', 'bar', null )).toBeFalse() })
    Typescript test typescript import {propEq} from 'rambda' const property = 'foo' const numberProperty = 1 const value = 'bar' const obj = {[property]: value} const objWithNumberIndex = {[numberProperty]: value} describe('R.propEq', () => { it('happy', () => { const result = propEq(property, value, obj) result // $ExpectType boolean }) it('number is property', () => { const result = propEq(1, value, objWithNumberIndex) result // $ExpectType boolean }) it('with optional property', () => { interface MyType { optional?: string | number } const myObject: MyType = {} const valueToFind = '1111' // $ExpectError propEq('optional', valueToFind, myObject) // $ExpectError propEq('optional', valueToFind, myObject) }) it('imported from @types/ramda', () => { interface A { foo: string | null } const obj: A = { foo: 'bar', } const value = '' const result = propEq('foo', value)(obj) result // $ExpectType boolean // $ExpectError propEq('bar', value)(obj) }) })
    Rambda is faster than Ramda with 91.92% text const R = require('../../dist/rambda.js') const obj = { a : { c : 2 }, b : 1, } const propInput = 'b' const expected = { c : 2 } const propEq = [ { label : 'Rambda', fn : () => { R.propEq('a')(expected)(obj) R.propEq('a', expected)(obj) R.propEq( 'a', expected, obj ) }, }, { label : 'Ramda', fn : () => { Ramda.propEq('a')(expected)(obj) Ramda.propEq('a', expected)(obj) Ramda.propEq( 'a', expected, obj ) }, }, ]

    ---------------

    propIs

    
    propIs<C extends (...args: any[]) => any, K extends keyof any>(type: C, name: K, obj: any): obj is Record<K, ReturnType<C>>
    

    It returns true if property of obj is from target type.

    const obj = {a:1, b: 'foo'}
    
    const result = [
      R.propIs(Number, 'a', Record<string, unknown>),
      R.propIs(String, 'b', Record<string, unknown>),
      R.propIs(Number, 'b', Record<string, unknown>),
    ]
    // => [true, true, false]
    

    Try this R.propIs example in Rambda REPL

    All Typescript definitions typescript propIs<C extends (...args: any[]) => any, K extends keyof any>(type: C, name: K, obj: any): obj is Record<K, ReturnType<C>>; propIs<C extends new (...args: any[]) => any, K extends keyof any>(type: C, name: K, obj: any): obj is Record<K, InstanceType<C>>; propIs<C extends (...args: any[]) => any, K extends keyof any>(type: C, name: K): (obj: any) => obj is Record<K, ReturnType<C>>; propIs<C extends new (...args: any[]) => any, K extends keyof any>(type: C, name: K): (obj: any) => obj is Record<K, InstanceType<C>>; propIs<C extends (...args: any[]) => any>(type: C): { <K extends keyof any>(name: K, obj: any): obj is Record<K, ReturnType<C>>; <K extends keyof any>(name: K): (obj: any) => obj is Record<K, ReturnType<C>>; }; propIs<C extends new (...args: any[]) => any>(type: C): { <K extends keyof any>(name: K, obj: any): obj is Record<K, InstanceType<C>>; <K extends keyof any>(name: K): (obj: any) => obj is Record<K, InstanceType<C>>; };
    R.propIs source javascript import { curry } from './curry.js' import { is } from './is.js' function propIsFn( targetPrototype, property, obj ){ return is(targetPrototype, obj[ property ]) } export const propIs = curry(propIsFn)
    Tests javascript import { propIs } from './propIs.js' const obj = { a : 1, b : 'foo', } test('when true', () => { expect(propIs( Number, 'a', obj )).toBeTrue() expect(propIs( String, 'b', obj )).toBeTrue() }) test('when false', () => { expect(propIs( String, 'a', obj )).toBeFalse() expect(propIs( Number, 'b', obj )).toBeFalse() })
    Typescript test typescript import {propIs} from 'rambda' const property = 'a' const obj = {a: 1} describe('R.propIs', () => { it('happy', () => { const result = propIs(Number, property, obj) result // $ExpectType boolean }) it('curried', () => { const result = propIs(Number, property)(obj) result // $ExpectType boolean }) })

    ---------------

    propOr

    
    propOr<T, P extends string>(defaultValue: T, property: P, obj: Partial<Record<P, T>> | undefined): T
    

    It returns either defaultValue or the value of property in obj.

    const obj = {a: 1}
    const defaultValue = 'DEFAULT_VALUE'
    const property = 'a'
    
    const result = [
      R.propOr(defaultValue, property, Record<string, unknown>),
      R.propOr(defaultValue, 'foo', Record<string, unknown>)
    ]
    // => [1, 'DEFAULT_VALUE']
    

    Try this R.propOr example in Rambda REPL

    All Typescript definitions typescript propOr<T, P extends string>(defaultValue: T, property: P, obj: Partial<Record<P, T>> | undefined): T; propOr<T, P extends string>(defaultValue: T, property: P): (obj: Partial<Record<P, T>> | undefined) => T; propOr<T>(defaultValue: T): { <P extends string>(property: P, obj: Partial<Record<P, T>> | undefined): T; <P extends string>(property: P): (obj: Partial<Record<P, T>> | undefined) => T; }
    R.propOr source javascript import { curry } from './curry.js' import { defaultTo } from './defaultTo.js' function propOrFn( defaultValue, property, obj ){ if (!obj) return defaultValue return defaultTo(defaultValue, obj[ property ]) } export const propOr = curry(propOrFn)
    Tests javascript import { propOr } from './propOr.js' test('propOr (result)', () => { const obj = { a : 1 } expect(propOr( 'default', 'a', obj )).toEqual(1) expect(propOr( 'default', 'notExist', obj )).toEqual('default') expect(propOr( 'default', 'notExist', null )).toEqual('default') }) test('propOr (currying)', () => { const obj = { a : 1 } expect(propOr('default')('a', obj)).toEqual(1) expect(propOr('default', 'a')(obj)).toEqual(1) expect(propOr('default')('notExist', obj)).toEqual('default') expect(propOr('default', 'notExist')(obj)).toEqual('default') })
    Typescript test typescript import {propOr} from 'rambda' const obj = {foo: 'bar'} const property = 'foo' const fallback = 'fallback' describe('R.propOr', () => { it('happy', () => { const result = propOr(fallback, property, obj) result // $ExpectType string }) it('curry 1', () => { const result = propOr(fallback)(property, obj) result // $ExpectType string }) it('curry 2', () => { const result = propOr(fallback, property)(obj) result // $ExpectType string }) it('curry 3', () => { const result = propOr(fallback)(property)(obj) result // $ExpectType string }) })

    ---------------

    props

    
    props<P extends string, T>(propsToPick: P[], obj: Record<P, T>): T[]
    

    It takes list with properties propsToPick and returns a list with property values in obj.

    const result = R.props(
      ['a', 'b'], 
      {a:1, c:3}
    )
    // => [1, undefined]
    

    Try this R.props example in Rambda REPL

    All Typescript definitions typescript props<P extends string, T>(propsToPick: P[], obj: Record<P, T>): T[]; props<P extends string>(propsToPick: P[]): <T>(obj: Record<P, T>) => T[]; props<P extends string, T>(propsToPick: P[]): (obj: Record<P, T>) => T[];
    R.props source javascript import { _isArray } from './_internals/_isArray.js' import { mapArray } from './map.js' export function props(propsToPick, obj){ if (arguments.length === 1){ return _obj => props(propsToPick, _obj) } if (!_isArray(propsToPick)){ throw new Error('propsToPick is not a list') } return mapArray(prop => obj[ prop ], propsToPick) }
    Tests javascript import { props } from './props.js' const obj = { a : 1, b : 2, } const propsToPick = [ 'a', 'c' ] test('happy', () => { const result = props(propsToPick, obj) expect(result).toEqual([ 1, undefined ]) }) test('curried', () => { const result = props(propsToPick)(obj) expect(result).toEqual([ 1, undefined ]) }) test('wrong input', () => { expect(() => props(null)(obj)).toThrow() })
    Typescript test typescript import {props} from 'rambda' const obj = {a: 1, b: 2} describe('R.props', () => { it('happy', () => { const result = props(['a', 'b'], obj) result // $ExpectType number[] }) it('curried', () => { const result = props(['a', 'b'])(obj) result // $ExpectType number[] }) })

    ---------------

    propSatisfies

    
    propSatisfies<T>(predicate: Predicate<T>, property: string, obj: Record<string, T>): boolean
    

    It returns true if the object property satisfies a given predicate.

    const obj = {a: {b:1}}
    const property = 'a'
    const predicate = x => x?.b === 1
    
    const result = R.propSatisfies(predicate, property, Record<string, unknown>)
    // => true
    

    Try this R.propSatisfies example in Rambda REPL

    All Typescript definitions typescript propSatisfies<T>(predicate: Predicate<T>, property: string, obj: Record<string, T>): boolean; propSatisfies<T>(predicate: Predicate<T>, property: string): (obj: Record<string, T>) => boolean;
    R.propSatisfies source javascript import { curry } from './curry.js' import { prop } from './prop.js' function propSatisfiesFn( predicate, property, obj ){ return predicate(prop(property, obj)) } export const propSatisfies = curry(propSatisfiesFn)
    Tests javascript import {propSatisfies} from './propSatisfies' const obj = {a: 1} test('when true', () => { expect(propSatisfies(x => x > 0, 'a', obj)).toBeTrue() }) test('when false', () => { expect(propSatisfies(x => x < 0, 'a')(obj)).toBeFalse() })
    Typescript test typescript import {propSatisfies} from 'rambda' const obj = {a: 1} describe('R.propSatisfies', () => { it('happy', () => { const result = propSatisfies(x => x > 0, 'a', obj) result // $ExpectType boolean }) it('curried requires explicit type', () => { const result = propSatisfies<number>(x => x > 0, 'a')(obj) result // $ExpectType boolean }) })

    ---------------

    range

    
    range(startInclusive: number, endExclusive: number): number[]
    

    It returns list of numbers between startInclusive to endExclusive markers.

    R.range(0, 5)
    // => [0, 1, 2, 3, 4]
    

    Try this R.range example in Rambda REPL

    All Typescript definitions typescript range(startInclusive: number, endExclusive: number): number[]; range(startInclusive: number): (endExclusive: number) => number[];
    R.range source javascript export function range(start, end){ if (arguments.length === 1) return _end => range(start, _end) if (Number.isNaN(Number(start)) || Number.isNaN(Number(end))){ throw new TypeError('Both arguments to range must be numbers') } if (end < start) return [] const len = end - start const willReturn = Array(len) for (let i = 0; i < len; i++){ willReturn[ i ] = start + i } return willReturn }
    Tests javascript import { range } from './range.js' test('happy', () => { expect(range(0, 10)).toEqual([ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 ]) }) test('end range is bigger than start range', () => { expect(range(7, 3)).toEqual([]) expect(range(5, 5)).toEqual([]) }) test('with bad input', () => { const throwMessage = 'Both arguments to range must be numbers' expect(() => range('a', 6)).toThrowWithMessage(Error, throwMessage) expect(() => range(6, 'z')).toThrowWithMessage(Error, throwMessage) }) test('curry', () => { expect(range(0)(10)).toEqual([ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 ]) })
    Typescript test typescript import {range} from 'rambda' describe('R.range', () => { it('happy', () => { const result = range(1, 4) result // $ExpectType number[] }) it('curried', () => { const result = range(1)(4) result // $ExpectType number[] }) })
    Rambda is fastest. Ramda is 61.8% slower and Lodash is 57.44% slower text const R = require('../../dist/rambda.js') const start = 12 const end = 22 const range = [ { label : 'Rambda', fn : () => { R.range(start, end) }, }, { label : 'Ramda', fn : () => { Ramda.range(start, end) }, }, { label : 'Lodash', fn : () => { _.range(start, end) }, }, ]

    ---------------

    reduce

    
    reduce<T, TResult>(reducer: (prev: TResult, current: T, i: number) => TResult, initialValue: TResult, list: T[]): TResult
    

    :boom: It passes index of the list as third argument to reducer function.

    const list = [1, 2, 3]
    const initialValue = 10
    const reducer = (prev, current) => prev * current
    
    const result = R.reduce(reducer, initialValue, list)
    // => 60
    

    Try this R.reduce example in Rambda REPL

    All Typescript definitions typescript reduce<T, TResult>(reducer: (prev: TResult, current: T, i: number) => TResult, initialValue: TResult, list: T[]): TResult; reduce<T, TResult>(reducer: (prev: TResult, current: T) => TResult, initialValue: TResult, list: T[]): TResult; reduce<T, TResult>(reducer: (prev: TResult, current: T, i?: number) => TResult): (initialValue: TResult, list: T[]) => TResult; reduce<T, TResult>(reducer: (prev: TResult, current: T, i?: number) => TResult, initialValue: TResult): (list: T[]) => TResult;
    R.reduce source javascript import { _isArray } from './_internals/_isArray.js' import { _keys } from './_internals/_keys.js' import { curry } from './curry.js' export function reduceFn( reducer, acc, list ){ if (!_isArray(list)){ throw new TypeError('reduce: list must be array or iterable') } let index = 0 const len = list.length while (index < len){ acc = reducer( acc, list[ index ], index, list ) index++ } return acc } export const reduce = curry(reduceFn)
    Tests javascript import { reduce } from './reduce.js' const reducer = ( prev, current, i ) => { expect(i).toBeNumber() return prev + current } const initialValue = 1 const list = [ 1, 2, 3 ] const ERROR = 'reduce: list must be array or iterable' test('happy', () => { expect(reduce( reducer, initialValue, list )).toEqual(7) }) test('with object as iterable', () => { expect(() => reduce( reducer, initialValue, { a : 1, b : 2, } )).toThrowWithMessage(TypeError, ERROR) }) test('with undefined as iterable', () => { expect(() => reduce( reducer, 0, null )).toThrowWithMessage(TypeError, ERROR) })
    Typescript test typescript import {reduce} from 'rambda' describe('R.reduce', () => { it('happy', () => { const result = reduce<number, number>( (acc, elem) => { acc // $ExpectType number elem // $ExpectType number return acc + elem }, 1, [1, 2, 3] ) result // $ExpectType number }) it('with two types', () => { const result = reduce<number, string>( (acc, elem) => { acc // $ExpectType string elem // $ExpectType number return `${acc}${elem}` }, 'foo', [1, 2, 3] ) result // $ExpectType string }) it('with index', () => { const result = reduce<number, number>( (acc, elem, i) => { acc // $ExpectType number elem // $ExpectType number i // $ExpectType number return acc + elem }, 1, [1, 2, 3] ) result // $ExpectType number }) it('fallback', () => { const result = reduce( (acc, val) => { acc // $ExpectType number return acc + val }, 1, [1, 2, 3] ) result // $ExpectType number }) it('fallback with index', () => { const result = reduce( (acc, val, i) => { acc // $ExpectType number i // $ExpectType number return acc + val }, 1, [1, 2, 3] ) result // $ExpectType number }) it('fallback with two types', () => { const result = reduce( (acc, val) => { acc // $ExpectType string return acc + val }, 'foo', [1, 2, 3] ) result // $ExpectType string }) })
    Lodash is fastest. Rambda is 60.48% slower and Ramda is 77.1% slower text const R = require('../../dist/rambda.js') const fn = (acc, value) => acc + value const holder = [ 1, 2, 3 ] const acc = '' const reduce = [ { label : 'Rambda', fn : () => { R.reduce( fn, acc, holder ) }, }, { label : 'Ramda', fn : () => { Ramda.reduce( fn, acc, holder ) }, }, { label : 'Lodash', fn : () => { _.reduce( holder, fn, acc ) }, }, ]

    ---------------

    reject

    
    reject<T>(predicate: Predicate<T>, list: T[]): T[]
    

    It has the opposite effect of R.filter.

    const list = [1, 2, 3, 4]
    const obj = {a: 1, b: 2}
    const predicate = x => x > 1
    
    const result = [
      R.reject(predicate, list),
      R.reject(predicate, Record<string, unknown>)
    ]
    // => [[1], {a: 1}]
    

    Try this R.reject example in Rambda REPL

    All Typescript definitions typescript reject<T>(predicate: Predicate<T>, list: T[]): T[]; reject<T>(predicate: Predicate<T>): (list: T[]) => T[]; reject<T>(predicate: Predicate<T>, obj: Dictionary<T>): Dictionary<T>; reject<T, U>(predicate: Predicate<T>): (obj: Dictionary<T>) => Dictionary<T>;
    R.reject source javascript import { filter } from './filter.js' export function reject(predicate, list){ if (arguments.length === 1) return _list => reject(predicate, _list) return filter(x => !predicate(x), list) }
    Tests javascript import { reject } from './reject.js' const isOdd = n => n % 2 === 1 test('with array', () => { expect(reject(isOdd)([ 1, 2, 3, 4 ])).toEqual([ 2, 4 ]) }) test('with object', () => { const obj = { a : 1, b : 2, c : 3, d : 4, } expect(reject(isOdd, obj)).toEqual({ b : 2, d : 4, }) })
    Typescript test typescript import {reject} from 'rambda' describe('R.reject with array', () => { it('happy', () => { const result = reject( x => { x // $ExpectType number return x > 1 }, [1, 2, 3] ) result // $ExpectType number[] }) it('curried require explicit type', () => { const result = reject<number>(x => { x // $ExpectType number return x > 1 })([1, 2, 3]) result // $ExpectType number[] }) }) describe('R.reject with objects', () => { it('happy', () => { const result = reject( x => { x // $ExpectType number return x > 1 }, {a: 1, b: 2} ) result // $ExpectType Dictionary<number> }) it('curried require dummy type', () => { const result = reject<number, any>(x => { return x > 1 })({a: 1, b: 2}) result // $ExpectType Dictionary<number> }) })

    ---------------

    repeat

    
    repeat<T>(x: T): (timesToRepeat: number) => T[]
    
    R.repeat('foo', 3)
    // => ['foo', 'foo', 'foo']
    

    Try this R.repeat example in Rambda REPL

    All Typescript definitions typescript repeat<T>(x: T): (timesToRepeat: number) => T[]; repeat<T>(x: T, timesToRepeat: number): T[];
    R.repeat source javascript export function repeat(x, timesToRepeat){ if (arguments.length === 1){ return _timesToRepeat => repeat(x, _timesToRepeat) } return Array(timesToRepeat).fill(x) }
    Tests javascript import { repeat } from './repeat.js' test('repeat', () => { expect(repeat('')(3)).toEqual([ '', '', '' ]) expect(repeat('foo', 3)).toEqual([ 'foo', 'foo', 'foo' ]) const obj = {} const arr = repeat(obj, 3) expect(arr).toEqual([ {}, {}, {} ]) expect(arr[ 0 ] === arr[ 1 ]).toBeTrue() })
    Typescript test typescript import {repeat} from 'rambda' describe('R.repeat', () => { it('happy', () => { const result = repeat(4, 7) result // $ExpectType number[] }) it('curried', () => { const result = repeat(4)(7) result // $ExpectType number[] }) })
    Lodash is fastest. Rambda is 48.57% slower and Ramda is 68.98% slower text const R = require('../../dist/rambda.js') const num = 10 const str = 'foo' const repeat = [ { label : 'Rambda', fn : () => { R.repeat(str, num) }, }, { label : 'Ramda', fn : () => { Ramda.repeat(str, num) }, }, { label : 'Lodash', fn : () => { _.repeat(str, num) }, }, ]

    ---------------

    replace

    
    replace(strOrRegex: RegExp | string, replacer: string, str: string): string
    

    It replaces strOrRegex found in str with replacer.

    const strOrRegex = /o/g
    
    const result = R.replace(strOrRegex, '|0|', 'foo')
    // => 'f|0||0|'
    

    Try this R.replace example in Rambda REPL

    All Typescript definitions typescript replace(strOrRegex: RegExp | string, replacer: string, str: string): string; replace(strOrRegex: RegExp | string, replacer: string): (str: string) => string; replace(strOrRegex: RegExp | string): (replacer: string) => (str: string) => string;
    R.replace source javascript import { curry } from './curry.js' function replaceFn( pattern, replacer, str ){ return str.replace(pattern, replacer) } export const replace = curry(replaceFn)
    Tests javascript import { replace } from './replace.js' test('happy', () => { expect(replace( 'foo', 'yes', 'foo bar baz' )).toEqual('yes bar baz') }) test('1', () => { expect(replace(/\s/g)('|')('foo bar baz')).toEqual('foo|bar|baz') }) test('2', () => { expect(replace(/\s/g)('|', 'foo bar baz')).toEqual('foo|bar|baz') }) test('3', () => { expect(replace(/\s/g, '|')('foo bar baz')).toEqual('foo|bar|baz') })
    Typescript test typescript import {replace} from 'rambda' const str = 'foo bar foo' const replacer = 'bar' describe('R.replace', () => { it('happy', () => { const result = replace(/foo/g, replacer, str) result // $ExpectType string }) it('with string as search pattern', () => { const result = replace('foo', replacer, str) result // $ExpectType string }) }) describe('R.replace - curried', () => { it('happy', () => { const result = replace(/foo/g, replacer)(str) result // $ExpectType string }) it('with string as search pattern', () => { const result = replace('foo', replacer)(str) result // $ExpectType string }) })
    Lodash is fastest. Rambda is 33.45% slower and Ramda is 33.99% slower text const R = require('../../dist/rambda.js') const replace = [ { label : 'Rambda', fn : () => { R.replace( /\s/g, '|', 'foo bar baz' ) }, }, { label : 'Ramda', fn : () => { Ramda.replace( /\s/g, '|', 'foo bar baz' ) }, }, { label : 'Lodash', fn : () => { _.replace( 'foo bar baz', /\s/g, '|' ) }, }, ]

    ---------------

    reverse

    
    reverse<T>(input: T[]): T[]
    

    It returns a reversed copy of list or string input.

    const result = [
      R.reverse('foo'),
      R.reverse([1, 2, 3])
    ]
    // => ['oof', [3, 2, 1]
    

    Try this R.reverse example in Rambda REPL

    All Typescript definitions typescript reverse<T>(input: T[]): T[]; reverse(input: string): string;
    R.reverse source javascript export function reverse(listOrString){ if (typeof listOrString === 'string'){ return listOrString.split('').reverse() .join('') } const clone = listOrString.slice() return clone.reverse() }
    Tests javascript import { reverse } from './reverse.js' test('happy', () => { expect(reverse([ 1, 2, 3 ])).toEqual([ 3, 2, 1 ]) }) test('with string', () => { expect(reverse('baz')).toEqual('zab') }) test('it doesn\'t mutate', () => { const arr = [ 1, 2, 3 ] expect(reverse(arr)).toEqual([ 3, 2, 1 ]) expect(arr).toEqual([ 1, 2, 3 ]) })
    Typescript test typescript import {reverse} from 'rambda' const list = [1, 2, 3, 4, 5] describe('R.reverse', () => { it('happy', () => { const result = reverse(list) result // $ExpectType number[] }) })

    ---------------

    set

    
    set<T, U>(lens: Lens, replacer: U, obj: T): T
    

    It returns a copied Object or Array with modified lens focus set to replacer value.

    const input = {x: 1, y: 2}
    const xLens = R.lensProp('x')
    
    const result = [
      R.set(xLens, 4, input),
      R.set(xLens, 8, input) 
    ]
    // => [{x: 4, y: 2}, {x: 8, y: 2}]
    

    Try this R.set example in Rambda REPL

    All Typescript definitions typescript set<T, U>(lens: Lens, replacer: U, obj: T): T; set<U>(lens: Lens, replacer: U): <T>(obj: T) => T; set(lens: Lens): <T, U>(replacer: U, obj: T) => T;
    R.set source javascript import { always } from './always.js' import { curry } from './curry.js' import { over } from './over.js' function setFn( lens, replacer, x ){ return over( lens, always(replacer), x ) } export const set = curry(setFn)
    Tests javascript import { assoc } from './assoc.js' import { lens } from './lens.js' import { lensIndex } from './lensIndex.js' import { lensPath } from './lensPath.js' import { prop } from './prop.js' import { set } from './set.js' const testObject = { foo : 'bar', baz : { a : 'x', b : 'y', }, } test('assoc lens', () => { const assocLens = lens(prop('foo'), assoc('foo')) const result = set( assocLens, 'FOO', testObject ) const expected = { ...testObject, foo : 'FOO', } expect(result).toEqual(expected) }) test('path lens', () => { const pathLens = lensPath('baz.a') const result = set( pathLens, 'z', testObject ) const expected = { ...testObject, baz : { a : 'z', b : 'y', }, } expect(result).toEqual(expected) }) test('index lens', () => { const indexLens = lensIndex(0) const result = set( indexLens, 3, [ 1, 2 ] ) expect(result).toEqual([ 3, 2 ]) })
    Rambda is faster than Ramda with 50.35% text const R = require('../../dist/rambda.js') const testObj = { a : 1 } const last = [ { label : 'Rambda', fn : () => { R.set( R.lensProp('a'), 2, testObj ) }, }, { label : 'Ramda', fn : () => { Ramda.set( Ramda.lensProp('a'), 2, testObj ) }, }, ]

    ---------------

    slice

    
    slice(from: number, to: number, input: string): string
    
    const list = [0, 1, 2, 3, 4, 5]
    const str = 'FOO_BAR'
    const from = 1
    const to = 4
    
    const result = [
      R.slice(from, to, str),
      R.slice(from, to, list)
    ]
    // => ['OO_', [1, 2, 3]]
    

    Try this R.slice example in Rambda REPL

    All Typescript definitions typescript slice(from: number, to: number, input: string): string; slice<T>(from: number, to: number, input: T[]): T[]; slice(from: number, to: number): { (input: string): string; <T>(input: T[]): T[]; }; slice(from: number): { (to: number, input: string): string; <T>(to: number, input: T[]): T[]; };
    R.slice source javascript import { curry } from './curry.js' function sliceFn( from, to, list ){ return list.slice(from, to) } export const slice = curry(sliceFn)
    Tests javascript import { slice } from './slice.js' test('slice', () => { expect(slice( 1, 3, [ 'a', 'b', 'c', 'd' ] )).toEqual([ 'b', 'c' ]) expect(slice( 1, Infinity, [ 'a', 'b', 'c', 'd' ] )).toEqual([ 'b', 'c', 'd' ]) expect(slice( 0, -1, [ 'a', 'b', 'c', 'd' ] )).toEqual([ 'a', 'b', 'c' ]) expect(slice( -3, -1, [ 'a', 'b', 'c', 'd' ] )).toEqual([ 'b', 'c' ]) expect(slice( 0, 3, 'ramda' )).toEqual('ram') })
    Typescript test typescript import {slice} from 'rambda' const list = [1, 2, 3, 4, 5] describe('R.slice', () => { it('happy', () => { const result = slice(1, 3, list) result // $ExpectType number[] }) it('curried', () => { const result = slice(1, 3)(list) result // $ExpectType number[] }) })

    ---------------

    sort

    
    sort<T>(sortFn: (a: T, b: T) => number, list: T[]): T[]
    

    It returns copy of list sorted by sortFn function, where sortFn needs to return only -1, 0 or 1.

    const list = [
      {a: 2},
      {a: 3},
      {a: 1}
    ]
    const sortFn = (x, y) => {
      return x.a > y.a ? 1 : -1
    }
    
    const result = R.sort(sortFn, list)
    const expected = [
      {a: 1},
      {a: 2},
      {a: 3}
    ]
    // => `result` is equal to `expected`
    

    Try this R.sort example in Rambda REPL

    All Typescript definitions typescript sort<T>(sortFn: (a: T, b: T) => number, list: T[]): T[]; sort<T>(sortFn: (a: T, b: T) => number): (list: T[]) => T[];
    R.sort source javascript import { cloneList } from './_internals/cloneList.js' export function sort(sortFn, list){ if (arguments.length === 1) return _list => sort(sortFn, _list) return cloneList(list).sort(sortFn) }
    Tests javascript import { sort } from './sort.js' const fn = (a, b) => a > b ? 1 : -1 test('sort', () => { expect(sort((a, b) => a - b)([ 2, 3, 1 ])).toEqual([ 1, 2, 3 ]) }) test('it doesn\'t mutate', () => { const list = [ 'foo', 'bar', 'baz' ] expect(sort(fn, list)).toEqual([ 'bar', 'baz', 'foo' ]) expect(list[ 0 ]).toBe('foo') expect(list[ 1 ]).toBe('bar') expect(list[ 2 ]).toBe('baz') })
    Typescript test typescript import {sort} from 'rambda' const list = [3, 0, 5, 2, 1] function sortFn(a: number, b: number): number { return a > b ? 1 : -1 } describe('R.sort', () => { it('happy', () => { const result = sort(sortFn, list) result // $ExpectType number[] }) it('curried', () => { const result = sort(sortFn)(list) result // $ExpectType number[] }) })
    Rambda is faster than Ramda with 40.23% text const R = require('../../dist/rambda.js') const list = [ 'foo', 'bar', 'baz' ] const fn = (a, b) => a > b ? -1 : 1 const replace = [ { label : 'Rambda', fn : () => { R.sort(fn, list) R.sort(fn)(list) }, }, { label : 'Ramda', fn : () => { Ramda.sort(fn, list) Ramda.sort(fn)(list) }, }, ]

    ---------------

    sortBy

    
    sortBy<T>(sortFn: (a: T) => Ord, list: T[]): T[]
    

    It returns copy of list sorted by sortFn function, where sortFn function returns a value to compare, i.e. it doesn't need to return only -1, 0 or 1.

    const list = [
      {a: 2},
      {a: 3},
      {a: 1}
    ]
    const sortFn = x => x.a
    
    const result = R.sortBy(sortFn, list)
    const expected = [
      {a: 1},
      {a: 2},
      {a: 3}
    ]
    // => `result` is equal to `expected`
    

    Try this R.sortBy example in Rambda REPL

    All Typescript definitions typescript sortBy<T>(sortFn: (a: T) => Ord, list: T[]): T[]; sortBy<T>(sortFn: (a: T) => Ord): (list: T[]) => T[]; sortBy(sortFn: (a: any) => Ord): <T>(list: T[]) => T[];
    R.sortBy source javascript import { cloneList } from './_internals/cloneList.js' export function sortBy(sortFn, list){ if (arguments.length === 1) return _list => sortBy(sortFn, _list) const clone = cloneList(list) return clone.sort((a, b) => { const aSortResult = sortFn(a) const bSortResult = sortFn(b) if (aSortResult === bSortResult) return 0 return aSortResult < bSortResult ? -1 : 1 }) }
    Tests javascript import { compose } from './compose.js' import { prop } from './prop.js' import { sortBy } from './sortBy.js' import { toLower } from './toLower.js' test('happy', () => { const input = [ { a : 2 }, { a : 1 }, { a : 1 }, { a : 3 } ] const expected = [ { a : 1 }, { a : 1 }, { a : 2 }, { a : 3 } ] const result = sortBy(x => x.a)(input) expect(result).toEqual(expected) }) test('with compose', () => { const alice = { name : 'ALICE', age : 101, } const bob = { name : 'Bob', age : -10, } const clara = { name : 'clara', age : 314.159, } const people = [ clara, bob, alice ] const sortByNameCaseInsensitive = sortBy(compose(toLower, prop('name'))) expect(sortByNameCaseInsensitive(people)).toEqual([ alice, bob, clara ]) })
    Typescript test typescript import {sortBy, pipe} from 'rambda' interface Input { a: number } describe('R.sortBy', () => { it('passing type to sort function', () => { function fn(x: any): number { return x.a } function fn2(x: Input): number { return x.a } const input = [{a: 2}, {a: 1}, {a: 0}] const result = sortBy(fn, input) const curriedResult = sortBy(fn2)(input) result // $ExpectType { a: number; }[] curriedResult // $ExpectType Input[] result[0].a // $ExpectType number curriedResult[0].a // $ExpectType number }) it('passing type to sort function and list', () => { function fn(x: Input): number { return x.a } const input: Input[] = [{a: 2}, {a: 1}, {a: 0}] const result = sortBy(fn, input) const curriedResult = sortBy(fn)(input) result // $ExpectType Input[] curriedResult // $ExpectType Input[] result[0].a // $ExpectType number }) it('with R.pipe', () => { interface Obj { value: number } const fn = pipe(sortBy<Obj>(x => x.value)) const result = fn([{value: 1}, {value: 2}]) result // $ExpectType Obj[] }) })
    Rambda is fastest. Ramda is 25.29% slower and Lodash is 56.88% slower text const R = require('../../dist/rambda.js') const list = [ { a : 2 }, { a : 1 }, { a : 0 } ] const fn = x => x.a const replace = [ { label : 'Rambda', fn : () => { R.sortBy(fn, list) }, }, { label : 'Ramda', fn : () => { Ramda.sortBy(fn, list) }, }, { label : 'Lodash', fn : () => { _.sortBy(list, fn) }, }, ]

    ---------------

    split

    
    split(separator: string | RegExp): (str: string) => string[]
    

    Curried version of String.prototype.split

    const str = 'foo|bar|baz'
    const separator = '|'
    const result = R.split(separator, str)
    // => [ 'foo', 'bar', 'baz' ]
    

    Try this R.split example in Rambda REPL

    All Typescript definitions typescript split(separator: string | RegExp): (str: string) => string[]; split(separator: string | RegExp, str: string): string[];
    R.split source javascript export function split(separator, str){ if (arguments.length === 1) return _str => split(separator, _str) return str.split(separator) }
    Tests javascript import { split } from './split.js' const str = 'foo|bar|baz' const splitChar = '|' const expected = [ 'foo', 'bar', 'baz' ] test('happy', () => { expect(split(splitChar, str)).toEqual(expected) }) test('curried', () => { expect(split(splitChar)(str)).toEqual(expected) })
    Typescript test typescript import {split} from 'rambda' const str = 'foo|bar|baz' const splitChar = '|' describe('R.split', () => { it('happy', () => { const result = split(splitChar, str) result // $ExpectType string[] }) it('curried', () => { const result = split(splitChar)(str) result // $ExpectType string[] }) })
    Rambda is fastest. Ramda is 55.37% slower and Lodash is 17.64% slower text const R = require('../../dist/rambda.js') const str = 'foo|bar|baz' const sep = '|' const split = [ { label : 'Rambda', fn : () => { R.split(sep, str) }, }, { label : 'Ramda', fn : () => { Ramda.split(sep, str) }, }, { label : 'Lodash', fn : () => { _.split(str, sep) }, }, ]

    ---------------

    splitAt

    
    splitAt<T>(index: number, input: T[]): [T[], T[]]
    

    It splits string or array at a given index.

    const list = [ 1, 2, 3 ]
    const result = R.splitAt(2, list)
    // => [[ 1, 2 ], [ 3 ]]
    

    Try this R.splitAt example in Rambda REPL

    All Typescript definitions typescript splitAt<T>(index: number, input: T[]): [T[], T[]]; splitAt(index: number, input: string): [string, string]; splitAt(index: number): { <T>(input: T[]): [T[], T[]]; (input: string): [string, string]; };
    R.splitAt source javascript import { _isArray } from './_internals/_isArray.js' import { drop } from './drop.js' import { maybe } from './maybe.js' import { take } from './take.js' export function splitAt(index, input){ if (arguments.length === 1){ return _list => splitAt(index, _list) } if (!input) throw new TypeError(`Cannot read property 'slice' of ${ input }`) if (!_isArray(input) && typeof input !== 'string') return [ [], [] ] const correctIndex = maybe( index < 0, input.length + index < 0 ? 0 : input.length + index, index ) return [ take(correctIndex, input), drop(correctIndex, input) ] }
    Tests javascript import { splitAt as splitAtRamda } from 'ramda' import { splitAt } from './splitAt.js' const list = [ 1, 2, 3 ] const str = 'foo bar' test('with array', () => { const result = splitAt(2, list) expect(result).toEqual([ [ 1, 2 ], [ 3 ] ]) }) test('with array - index is negative number', () => { const result = splitAt(-6, list) expect(result).toEqual([ [], list ]) }) test('with array - index is out of scope', () => { const result = splitAt(4, list) expect(result).toEqual([ [ 1, 2, 3 ], [] ]) }) test('with string', () => { const result = splitAt(4, str) expect(result).toEqual([ 'foo ', 'bar' ]) }) test('with string - index is negative number', () => { const result = splitAt(-2, str) expect(result).toEqual([ 'foo b', 'ar' ]) }) test('with string - index is out of scope', () => { const result = splitAt(10, str) expect(result).toEqual([ str, '' ]) }) test('with array - index is out of scope', () => { const result = splitAt(4)(list) expect(result).toEqual([ [ 1, 2, 3 ], [] ]) }) const badInputs = [ 1, true, /foo/g, {} ] const throwingBadInputs = [ null, undefined ] test('with bad inputs', () => { throwingBadInputs.forEach(badInput => { expect(() => splitAt(1, badInput)).toThrowWithMessage(TypeError, `Cannot read property 'slice' of ${ badInput }`) expect(() => splitAtRamda(1, badInput)).toThrowWithMessage(TypeError, `Cannot read properties of ${ badInput } (reading 'slice')`) }) badInputs.forEach(badInput => { const result = splitAt(1, badInput) const ramdaResult = splitAtRamda(1, badInput) expect(result).toEqual(ramdaResult) }) })
    Typescript test typescript import {splitAt} from 'ramda' const index = 1 const str = 'foo' const list = [1, 2, 3] describe('R.splitAt with array', () => { it('happy', () => { const result = splitAt(index, list) result // $ExpectType [number[], number[]] }) it('curried', () => { const result = splitAt(index)(list) result // $ExpectType [number[], number[]] }) }) describe('R.splitAt with string', () => { it('happy', () => { const result = splitAt(index, str) result // $ExpectType [string, string] }) it('curried', () => { const result = splitAt(index)(str) result // $ExpectType [string, string] }) })

    ---------------

    splitEvery

    
    splitEvery<T>(sliceLength: number, input: T[]): (T[])[]
    

    It splits input into slices of sliceLength.

    const result = [
      R.splitEvery(2, [1, 2, 3]), 
      R.splitEvery(3, 'foobar') 
    ]
    
    const expected = [
      [[1, 2], [3]],
      ['foo', 'bar']
    ]
    // => `result` is equal to `expected`
    

    Try this R.splitEvery example in Rambda REPL

    All Typescript definitions typescript splitEvery<T>(sliceLength: number, input: T[]): (T[])[]; splitEvery(sliceLength: number, input: string): string[]; splitEvery(sliceLength: number): { (input: string): string[]; <T>(input: T[]): (T[])[]; };
    R.splitEvery source javascript export function splitEvery(sliceLength, listOrString){ if (arguments.length === 1){ return _listOrString => splitEvery(sliceLength, _listOrString) } if (sliceLength < 1){ throw new Error('First argument to splitEvery must be a positive integer') } const willReturn = [] let counter = 0 while (counter < listOrString.length){ willReturn.push(listOrString.slice(counter, counter += sliceLength)) } return willReturn }
    Tests javascript import { splitEvery } from './splitEvery.js' test('happy', () => { expect(splitEvery(3, [ 1, 2, 3, 4, 5, 6, 7 ])).toEqual([ [ 1, 2, 3 ], [ 4, 5, 6 ], [ 7 ], ]) expect(splitEvery(3)('foobarbaz')).toEqual([ 'foo', 'bar', 'baz' ]) }) test('with bad input', () => { expect(() => expect(splitEvery(0)('foo')).toEqual([ 'f', 'o', 'o' ])).toThrowWithMessage(Error, 'First argument to splitEvery must be a positive integer') })
    Typescript test typescript import {splitEvery} from 'rambda' const list = [1, 2, 3, 4, 5, 6, 7] describe('R.splitEvery', () => { it('happy', () => { const result = splitEvery(3, list) result // $ExpectType number[][] }) it('curried', () => { const result = splitEvery(3)(list) result // $ExpectType number[][] }) })
    Rambda is faster than Ramda with 71.98% text const R = require('../../dist/rambda.js') const list = [ 1, 2, 3, 4, 5, 6, 7 ] const splitEvery = [ { label : 'Rambda', fn : () => { R.splitEvery(3, list) }, }, { label : 'Ramda', fn : () => { Ramda.splitEvery(3, list) }, }, ]

    ---------------

    splitWhen

    
    splitWhen<T, U>(predicate: Predicate<T>, list: U[]): (U[])[]
    

    It splits list to two arrays according to a predicate function.

    The first array contains all members of list before predicate returns true.

    const list = [1, 2, 1, 2]
    const result = R.splitWhen(R.equals(2), list)
    // => [[1], [2, 1, 2]]
    

    Try this R.splitWhen example in Rambda REPL

    All Typescript definitions typescript splitWhen<T, U>(predicate: Predicate<T>, list: U[]): (U[])[]; splitWhen<T>(predicate: Predicate<T>): <U>(list: U[]) => (U[])[];
    R.splitWhen source javascript export function splitWhen(predicate, input){ if (arguments.length === 1){ return _input => splitWhen(predicate, _input) } if (!input) throw new TypeError(`Cannot read property 'length' of ${ input }`) const preFound = [] const postFound = [] let found = false let counter = -1 while (counter++ < input.length - 1){ if (found){ postFound.push(input[ counter ]) } else if (predicate(input[ counter ])){ postFound.push(input[ counter ]) found = true } else { preFound.push(input[ counter ]) } } return [ preFound, postFound ] }
    Tests javascript import { splitWhen as splitWhenRamda } from 'ramda' import { equals } from './equals.js' import { splitWhen } from './splitWhen.js' const list = [ 1, 2, 1, 2 ] test('happy', () => { const result = splitWhen(equals(2), list) expect(result).toEqual([ [ 1 ], [ 2, 1, 2 ] ]) }) test('when predicate returns false', () => { const result = splitWhen(equals(3))(list) expect(result).toEqual([ list, [] ]) }) const badInputs = [ 1, true, /foo/g, {} ] const throwingBadInputs = [ null, undefined ] test('with bad inputs', () => { throwingBadInputs.forEach(badInput => { expect(() => splitWhen(equals(2), badInput)).toThrowWithMessage(TypeError, `Cannot read property 'length' of ${ badInput }`) expect(() => splitWhenRamda(equals(2), badInput)).toThrowWithMessage(TypeError, `Cannot read properties of ${ badInput } (reading 'length')`) }) badInputs.forEach(badInput => { const result = splitWhen(equals(2), badInput) const ramdaResult = splitWhenRamda(equals(2), badInput) expect(result).toEqual(ramdaResult) }) })
    Typescript test typescript import {splitWhen} from 'rambda' const list = [1, 2, 1, 2] const predicate = (x: number) => x === 2 describe('R.splitWhen', () => { it('happy', () => { const result = splitWhen(predicate, list) result // $ExpectType number[][] }) it('curried', () => { const result = splitWhen(predicate)(list) result // $ExpectType number[][] }) })

    ---------------

    startsWith

    
    startsWith(target: string, str: string): boolean
    

    When iterable is a string, then it behaves as String.prototype.startsWith. When iterable is a list, then it uses R.equals to determine if the target list starts in the same way as the given target.

    :boom: It doesn't work with arrays unlike its corresponding Ramda method.

    const str = 'foo-bar'
    const list = [{a:1}, {a:2}, {a:3}]
    
    const result = [
      R.startsWith('foo', str),
      R.startsWith([{a:1}, {a:2}], list)
    ]
    // => [true, true]
    

    Try this R.startsWith example in Rambda REPL

    All Typescript definitions typescript startsWith(target: string, str: string): boolean; startsWith(target: string): (str: string) => boolean; startsWith<T>(target: T[], list: T[]): boolean; startsWith<T>(target: T[]): (list: T[]) => boolean;
    R.startsWith source javascript import { _isArray } from './_internals/_isArray.js' import { equals } from './equals.js' export function startsWith(target, iterable){ if (arguments.length === 1) return _iterable => startsWith(target, _iterable) if (typeof iterable === 'string'){ return iterable.startsWith(target) } if (!_isArray(target)) return false let correct = true const filtered = target.filter((x, index) => { if (!correct) return false const result = equals(x, iterable[ index ]) if (!result) correct = false return result }) return filtered.length === target.length }
    Tests javascript import { startsWith as startsWithRamda } from 'ramda' import { compareCombinations } from './_internals/testUtils.js' import { possibleIterables, possibleTargets } from './endsWith.spec.js' import { startsWith } from './startsWith.js' test('with string', () => { expect(startsWith('foo', 'foo-bar')).toBeTrue() expect(startsWith('baz')('foo-bar')).toBeFalse() }) test('use R.equals with array', () => { const list = [ { a : 1 }, { a : 2 }, { a : 3 } ] expect(startsWith({ a : 1 }, list)).toBeFalse() expect(startsWith([ { a : 1 } ], list)).toBeTrue() expect(startsWith([ { a : 1 }, { a : 2 } ], list)).toBeTrue() expect(startsWith(list, list)).toBeTrue() expect(startsWith([ { a : 2 } ], list)).toBeFalse() }) describe('brute force', () => { compareCombinations({ fn : startsWith, fnRamda : startsWithRamda, firstInput : possibleTargets, secondInput : possibleIterables, callback : errorsCounters => { expect(errorsCounters).toMatchInlineSnapshot(` Object { "ERRORS_MESSAGE_MISMATCH": 0, "ERRORS_TYPE_MISMATCH": 0, "RESULTS_MISMATCH": 0, "SHOULD_NOT_THROW": 0, "SHOULD_THROW": 0, "TOTAL_TESTS": 32, } `) }, }) })
    Typescript test typescript import {startsWith} from 'rambda' describe('R.startsWith - array as iterable', () => { const target = [{a: 1}] const iterable = [{a: 1}, {a: 2}] it('happy', () => { const result = startsWith(target, iterable) result // $ExpectType boolean }) it('curried', () => { const result = startsWith(target)(iterable) result // $ExpectType boolean }) }) describe('R.startsWith - string as iterable', () => { const target = 'foo' const iterable = 'foo bar' it('happy', () => { const result = startsWith(target, iterable) result // $ExpectType boolean }) it('curried', () => { const result = startsWith(target)(iterable) result // $ExpectType boolean }) })

    ---------------

    subtract

    Curried version of x - y

    const x = 3
    const y = 1
    
    const result = R.subtract(x, y) 
    // => 2
    

    Try this R.subtract example in Rambda REPL

    ---------------

    sum

    
    sum(list: number[]): number
    
    R.sum([1, 2, 3, 4, 5]) 
    // => 15
    

    Try this R.sum example in Rambda REPL

    All Typescript definitions typescript sum(list: number[]): number;
    R.sum source javascript export function sum(list){ return list.reduce((prev, current) => prev + current, 0) }
    Tests javascript import { sum } from './sum.js' test('happy', () => { expect(sum([ 1, 2, 3, 4, 5 ])).toBe(15) })

    ---------------

    symmetricDifference

    
    symmetricDifference<T>(x: T[], y: T[]): T[]
    

    It returns a merged list of x and y with all equal elements removed.

    R.equals is used to determine equality.

    const x = [ 1, 2, 3, 4 ]
    const y = [ 3, 4, 5, 6 ]
    
    const result = R.symmetricDifference(x, y)
    // => [ 1, 2, 5, 6 ]
    

    Try this R.symmetricDifference example in Rambda REPL

    All Typescript definitions typescript symmetricDifference<T>(x: T[], y: T[]): T[]; symmetricDifference<T>(x: T[]): <T>(y: T[]) => T[];
    R.symmetricDifference source javascript import { concat } from './concat.js' import { filter } from './filter.js' import { includes } from './includes.js' export function symmetricDifference(x, y){ if (arguments.length === 1){ return _y => symmetricDifference(x, _y) } return concat(filter(value => !includes(value, y), x), filter(value => !includes(value, x), y)) }
    Tests javascript import { symmetricDifference } from './symmetricDifference.js' test('symmetricDifference', () => { const list1 = [ 1, 2, 3, 4 ] const list2 = [ 3, 4, 5, 6 ] expect(symmetricDifference(list1)(list2)).toEqual([ 1, 2, 5, 6 ]) expect(symmetricDifference([], [])).toEqual([]) }) test('symmetricDifference with objects', () => { const list1 = [ { id : 1 }, { id : 2 }, { id : 3 }, { id : 4 } ] const list2 = [ { id : 3 }, { id : 4 }, { id : 5 }, { id : 6 } ] expect(symmetricDifference(list1)(list2)).toEqual([ { id : 1 }, { id : 2 }, { id : 5 }, { id : 6 }, ]) })
    Typescript test typescript import {symmetricDifference} from 'rambda' describe('R.symmetricDifference', () => { it('happy', () => { const list1 = [1, 2, 3, 4] const list2 = [3, 4, 5, 6] const result = symmetricDifference(list1, list2) result // $ExpectType number[] }) it('curried', () => { const list1 = [{id: 1}, {id: 2}, {id: 3}, {id: 4}] const list2 = [{id: 3}, {id: 4}, {id: 5}, {id: 6}] const result = symmetricDifference(list1)(list2) result // $ExpectType { id: number; }[] }) })

    ---------------

    T

    
    T(): boolean
    
    R.T() 
    // => true
    

    Try this R.T example in Rambda REPL

    All Typescript definitions typescript T(): boolean;
    R.T source javascript export function T(){ return true }

    ---------------

    tail

    
    tail<T extends unknown[]>(input: T): T extends [any, ...infer U] ? U : [...T]
    

    It returns all but the first element of input.

    const result = [
      R.tail([1, 2, 3]),  
      R.tail('foo') 
    ]
    // => [[2, 3], 'oo']
    

    Try this R.tail example in Rambda REPL

    All Typescript definitions typescript tail<T extends unknown[]>(input: T): T extends [any, ...infer U] ? U : [...T]; tail(input: string): string;
    R.tail source javascript import { drop } from './drop.js' export function tail(listOrString){ return drop(1, listOrString) }
    Tests javascript import { tail } from './tail.js' test('tail', () => { expect(tail([ 1, 2, 3 ])).toEqual([ 2, 3 ]) expect(tail([ 1, 2 ])).toEqual([ 2 ]) expect(tail([ 1 ])).toEqual([]) expect(tail([])).toEqual([]) expect(tail('abc')).toEqual('bc') expect(tail('ab')).toEqual('b') expect(tail('a')).toEqual('') expect(tail('')).toEqual('') })
    Typescript test typescript import {tail} from 'rambda' describe('R.tail', () => { it('with string', () => { const result = tail('foo') result // $ExpectType string }) it('with list - one type', () => { const result = tail([1, 2, 3]) result // $ExpectType number[] }) it('with list - mixed types', () => { const result = tail(['foo', 'bar', 1, 2, 3]) result // $ExpectType (string | number)[] }) })

    ---------------

    take

    
    take<T>(howMany: number, input: T[]): T[]
    

    It returns the first howMany elements of input.

    const howMany = 2
    
    const result = [
      R.take(howMany, [1, 2, 3]),
      R.take(howMany, 'foobar'),
    ]
    // => [[1, 2], 'fo']
    

    Try this R.take example in Rambda REPL

    All Typescript definitions typescript take<T>(howMany: number, input: T[]): T[]; take(howMany: number, input: string): string; take<T>(howMany: number): { <T>(input: T[]): T[]; (input: string): string; };
    R.take source javascript import baseSlice from './_internals/baseSlice.js' export function take(howMany, listOrString){ if (arguments.length === 1) return _listOrString => take(howMany, _listOrString) if (howMany < 0) return listOrString.slice() if (typeof listOrString === 'string') return listOrString.slice(0, howMany) return baseSlice( listOrString, 0, howMany ) }
    Tests javascript import { take } from './take.js' test('happy', () => { const arr = [ 'foo', 'bar', 'baz' ] expect(take(1, arr)).toEqual([ 'foo' ]) expect(arr).toEqual([ 'foo', 'bar', 'baz' ]) expect(take(2)([ 'foo', 'bar', 'baz' ])).toEqual([ 'foo', 'bar' ]) expect(take(3, [ 'foo', 'bar', 'baz' ])).toEqual([ 'foo', 'bar', 'baz' ]) expect(take(4, [ 'foo', 'bar', 'baz' ])).toEqual([ 'foo', 'bar', 'baz' ]) expect(take(3)('rambda')).toEqual('ram') }) test('with negative index', () => { expect(take(-1, [ 1, 2, 3 ])).toEqual([ 1, 2, 3 ]) expect(take(-Infinity, [ 1, 2, 3 ])).toEqual([ 1, 2, 3 ]) }) test('with zero index', () => { expect(take(0, [ 1, 2, 3 ])).toEqual([]) })
    Typescript test typescript import {take} from 'rambda' const list = [1, 2, 3, 4] const str = 'foobar' const howMany = 2 describe('R.take - array', () => { it('happy', () => { const result = take(howMany, list) result // $ExpectType number[] }) it('curried', () => { const result = take(howMany)(list) result // $ExpectType number[] }) }) describe('R.take - string', () => { it('happy', () => { const result = take(howMany, str) result // $ExpectType string }) it('curried', () => { const result = take(howMany)(str) result // $ExpectType string }) })
    Rambda is fastest. Ramda is 91.96% slower and Lodash is 4.72% slower text const R = require('../../dist/rambda.js') const list = [ 1, 2, 3, 4 ] const num = 2 const take = [ { label : 'Rambda', fn : () => { R.take(num, list) }, }, { label : 'Ramda', fn : () => { Ramda.take(num, list) }, }, { label : 'Lodash', fn : () => { _.take(list, num) }, }, ]

    ---------------

    takeLast

    
    takeLast<T>(howMany: number, input: T[]): T[]
    

    It returns the last howMany elements of input.

    const howMany = 2
    
    const result = [
      R.takeLast(howMany, [1, 2, 3]),
      R.takeLast(howMany, 'foobar'),
    ]
    // => [[2, 3], 'ar']
    

    Try this R.takeLast example in Rambda REPL

    All Typescript definitions typescript takeLast<T>(howMany: number, input: T[]): T[]; takeLast(howMany: number, input: string): string; takeLast<T>(howMany: number): { <T>(input: T[]): T[]; (input: string): string; };
    R.takeLast source javascript import baseSlice from './_internals/baseSlice.js' export function takeLast(howMany, listOrString){ if (arguments.length === 1) return _listOrString => takeLast(howMany, _listOrString) const len = listOrString.length if (howMany < 0) return listOrString.slice() let numValue = howMany > len ? len : howMany if (typeof listOrString === 'string') return listOrString.slice(len - numValue) numValue = len - numValue return baseSlice( listOrString, numValue, len ) }
    Tests javascript import { takeLast } from './takeLast.js' test('with arrays', () => { expect(takeLast(1, [ 'foo', 'bar', 'baz' ])).toEqual([ 'baz' ]) expect(takeLast(2)([ 'foo', 'bar', 'baz' ])).toEqual([ 'bar', 'baz' ]) expect(takeLast(3, [ 'foo', 'bar', 'baz' ])).toEqual([ 'foo', 'bar', 'baz' ]) expect(takeLast(4, [ 'foo', 'bar', 'baz' ])).toEqual([ 'foo', 'bar', 'baz' ]) expect(takeLast(10, [ 'foo', 'bar', 'baz' ])).toEqual([ 'foo', 'bar', 'baz' ]) }) test('with strings', () => { expect(takeLast(3, 'rambda')).toEqual('bda') expect(takeLast(7, 'rambda')).toEqual('rambda') }) test('with negative index', () => { expect(takeLast(-1, [ 1, 2, 3 ])).toEqual([ 1, 2, 3 ]) expect(takeLast(-Infinity, [ 1, 2, 3 ])).toEqual([ 1, 2, 3 ]) })
    Typescript test typescript import {takeLast} from 'rambda' const list = [1, 2, 3, 4] const str = 'foobar' const howMany = 2 describe('R.takeLast - array', () => { it('happy', () => { const result = takeLast(howMany, list) result // $ExpectType number[] }) it('curried', () => { const result = takeLast(howMany)(list) result // $ExpectType number[] }) }) describe('R.takeLast - string', () => { it('happy', () => { const result = takeLast(howMany, str) result // $ExpectType string }) it('curried', () => { const result = takeLast(howMany)(str) result // $ExpectType string }) })
    Rambda is fastest. Ramda is 93.39% slower and Lodash is 19.22% slower text const R = require('../../dist/rambda.js') const list = [ 1, 2, 3, 4 ] const num = 2 const takeLast = [ { label : 'Rambda', fn : () => { R.takeLast(num, list) }, }, { label : 'Ramda', fn : () => { Ramda.takeLast(num, list) }, }, { label : 'Lodash', fn : () => { _.takeRight(list, num) }, }, ]

    ---------------

    takeLastWhile

    
    takeLastWhile(predicate: (x: string) => boolean, input: string): string
    
    const result = R.takeLastWhile(
      x => x > 2,
      [1, 2, 3, 4]
    )
    // => [3, 4]
    

    Try this R.takeLastWhile example in Rambda REPL

    All Typescript definitions typescript takeLastWhile(predicate: (x: string) => boolean, input: string): string; takeLastWhile(predicate: (x: string) => boolean): (input: string) => string; takeLastWhile<T>(predicate: (x: T) => boolean, input: T[]): T[]; takeLastWhile<T>(predicate: (x: T) => boolean): <T>(input: T[]) => T[];
    R.takeLastWhile source javascript import { _isArray } from './_internals/_isArray.js' export function takeLastWhile(predicate, input){ if (arguments.length === 1){ return _input => takeLastWhile(predicate, _input) } if (input.length === 0) return input let found = false const toReturn = [] let counter = input.length while (!found || counter === 0){ counter-- if (predicate(input[ counter ]) === false){ found = true } else if (!found){ toReturn.push(input[ counter ]) } } return _isArray(input) ? toReturn.reverse() : toReturn.reverse().join('') }
    Tests javascript import { takeLastWhile } from './takeLastWhile.js' const assert = require('assert') const list = [ 1, 2, 3, 4 ] test('happy', () => { const predicate = x => x > 2 const result = takeLastWhile(predicate, list) expect(result).toEqual([ 3, 4 ]) }) test('predicate is always true', () => { const predicate = x => x > 0 const result = takeLastWhile(predicate)(list) expect(result).toEqual(list) }) test('predicate is always false', () => { const predicate = x => x < 0 const result = takeLastWhile(predicate, list) expect(result).toEqual([]) }) test('with string', () => { const result = takeLastWhile(x => x !== 'F', 'FOOBAR') expect(result).toEqual('OOBAR') })
    Typescript test typescript import {takeLastWhile} from 'rambda' const list = [1, 2, 3] const str = 'FOO' describe('R.takeLastWhile', () => { it('with array', () => { const result = takeLastWhile(x => x > 1, list) result // $ExpectType number[] }) it('with array - curried', () => { const result = takeLastWhile(x => x > 1, list) result // $ExpectType number[] }) it('with string', () => { const result = takeLastWhile(x => x !== 'F', str) result // $ExpectType string }) it('with string - curried', () => { const result = takeLastWhile(x => x !== 'F')(str) result // $ExpectType string }) })

    ---------------

    takeWhile

    const list = [1, 2, 3, 4]
    const predicate = x => x < 3
    
    const result = R.takeWhile(predicate, list)
    // => [1, 2]
    

    Try this R.takeWhile example in Rambda REPL

    ---------------

    tap

    
    tap<T>(fn: (x: T) => void, input: T): T
    

    It applies function fn to input x and returns x.

    One use case is debuging in the middle of R.compose.

    const list = [1, 2, 3]
    
    R.compose(
      R.map(x => x * 2)
      R.tap(console.log),
      R.filter(x => x > 1)
    )(list)
    // => `2` and `3` will be logged
    

    Try this R.tap example in Rambda REPL

    All Typescript definitions typescript tap<T>(fn: (x: T) => void, input: T): T; tap<T>(fn: (x: T) => void): (input: T) => T;
    R.tap source javascript export function tap(fn, x){ if (arguments.length === 1) return _x => tap(fn, _x) fn(x) return x }
    Tests javascript import { tap } from './tap.js' test('tap', () => { let a = 1 const sayX = x => a = x expect(tap(sayX, 100)).toEqual(100) expect(tap(sayX)(100)).toEqual(100) expect(a).toEqual(100) })
    Typescript test typescript import {tap, pipe} from 'rambda' describe('R.tap', () => { it('happy', () => { pipe( tap(x => { x // $ExpectType number[] }), (x: number[]) => x.length )([1, 2]) }) })

    ---------------

    test

    
    test(regExpression: RegExp): (str: string) => boolean
    

    It determines whether str matches regExpression.

    R.test(/^f/, 'foo')
    // => true
    

    Try this R.test example in Rambda REPL

    All Typescript definitions typescript test(regExpression: RegExp): (str: string) => boolean; test(regExpression: RegExp, str: string): boolean;
    R.test source javascript export function test(pattern, str){ if (arguments.length === 1) return _str => test(pattern, _str) if (typeof pattern === 'string'){ throw new TypeError(`‘test’ requires a value of type RegExp as its first argument; received "${ pattern }"`) } return str.search(pattern) !== -1 }
    Tests javascript import { test as testMethod } from './test.js' test('happy', () => { expect(testMethod(/^x/, 'xyz')).toBeTrue() expect(testMethod(/^y/)('xyz')).toBeFalse() }) test('throws if first argument is not regex', () => { expect(() => testMethod('foo', 'bar')).toThrowWithMessage(TypeError, '‘test’ requires a value of type RegExp as its first argument; received "foo"') })
    Typescript test typescript import {test} from 'rambda' const input = 'foo ' const regex = /foo/ describe('R.test', () => { it('happy', () => { const result = test(regex, input) result // $ExpectType boolean }) it('curried', () => { const result = test(regex)(input) result // $ExpectType boolean }) })
    Rambda is faster than Ramda with 82.34% text const R = require('../../dist/rambda.js') const test = [ { label : 'Rambda', fn : () => { R.test(/\s/g, 'x y z') R.test(/\s/g)('x y z') }, }, { label : 'Ramda', fn : () => { Ramda.test(/\s/g, 'x y z') Ramda.test(/\s/g)('x y z') }, }, ]

    ---------------

    times

    
    times<T>(fn: (i: number) => T, howMany: number): T[]
    

    It returns the result of applying function fn over members of range array.

    The range array includes numbers between 0 and howMany(exclusive).

    const fn = x => x * 2
    const howMany = 5
    
    R.times(fn, howMany)
    // => [0, 2, 4, 6, 8]
    

    Try this R.times example in Rambda REPL

    All Typescript definitions typescript times<T>(fn: (i: number) => T, howMany: number): T[]; times<T>(fn: (i: number) => T): (howMany: number) => T[];
    R.times source javascript import { map } from './map.js' import { range } from './range.js' export function times(fn, howMany){ if (arguments.length === 1) return _howMany => times(fn, _howMany) if (!Number.isInteger(howMany) || howMany < 0){ throw new RangeError('n must be an integer') } return map(fn, range(0, howMany)) }
    Tests javascript import assert from 'assert' import { identity } from './identity.js' import { times } from './times.js' test('happy', () => { const result = times(identity, 5) expect(result).toEqual([ 0, 1, 2, 3, 4 ]) }) test('with bad input', () => { assert.throws(() => { times(3)('cheers!') }, RangeError) assert.throws(() => { times(identity, -1) }, RangeError) }) test('curry', () => { const result = times(identity)(5) expect(result).toEqual([ 0, 1, 2, 3, 4 ]) })
    Typescript test typescript import {times, identity} from 'rambda' describe('R.times', () => { it('happy', () => { const result = times(identity, 5) result // $ExpectType number[] }) })

    ---------------

    toLower

    
    toLower<S extends string>(str: S): Lowercase<S>
    
    R.toLower('FOO')
    // => 'foo'
    

    Try this R.toLower example in Rambda REPL

    All Typescript definitions typescript toLower<S extends string>(str: S): Lowercase<S>; toLower(str: string): string;
    R.toLower source javascript export function toLower(str){ return str.toLowerCase() }
    Tests javascript import { toLower } from './toLower.js' test('toLower', () => { expect(toLower('FOO|BAR|BAZ')).toEqual('foo|bar|baz') })

    ---------------

    toPairs

    
    toPairs<O extends object, K extends Extract<keyof O, string | number>>(obj: O): Array<{ [key in K]: [`${key}`, O[key]] }[K]>
    

    It transforms an object to a list.

    const list = {
      a : 1,
      b : 2,
      c : [ 3, 4 ],
    }
    const expected = [ [ 'a', 1 ], [ 'b', 2 ], [ 'c', [ 3, 4 ] ] ]
    
    const result = R.toPairs(list)
    // => `result` is equal to `expected`
    

    Try this R.toPairs example in Rambda REPL

    All Typescript definitions typescript toPairs<O extends object, K extends Extract<keyof O, string | number>>(obj: O): Array<{ [key in K]: [`${key}`, O[key]] }[K]>; toPairs<S>(obj: Record<string | number, S>): Array<[string, S]>;
    R.toPairs source javascript export function toPairs(obj){ return Object.entries(obj) }
    Tests javascript import { toPairs } from './toPairs.js' const obj = { a : 1, b : 2, c : [ 3, 4 ], } const expected = [ [ 'a', 1 ], [ 'b', 2 ], [ 'c', [ 3, 4 ] ], ] test('happy', () => { expect(toPairs(obj)).toEqual(expected) })
    Typescript test typescript import {toPairs} from 'rambda' const obj = { a: 1, b: 2, c: [3, 4], } describe('R.toPairs', () => { it('happy', () => { const result = toPairs(obj) result // $ExpectType (["b", number] | ["a", number] | ["c", number[]])[] }) })

    ---------------

    toString

    
    toString(x: unknown): string
    
    R.toString([1, 2]) 
    // => '1,2'
    

    Try this R.toString example in Rambda REPL

    All Typescript definitions typescript toString(x: unknown): string;
    R.toString source javascript export function toString(x){ return x.toString() }
    Tests javascript import { toString } from './toString.js' test('happy', () => { expect(toString([ 1, 2, 3 ])).toEqual('1,2,3') })

    ---------------

    toUpper

    
    toUpper<S extends string>(str: S): Uppercase<S>
    
    R.toUpper('foo')
    // => 'FOO'
    

    Try this R.toUpper example in Rambda REPL

    All Typescript definitions typescript toUpper<S extends string>(str: S): Uppercase<S>; toUpper(str: string): string;
    R.toUpper source javascript export function toUpper(str){ return str.toUpperCase() }
    Tests javascript import { toUpper } from './toUpper.js' test('toUpper', () => { expect(toUpper('foo|bar|baz')).toEqual('FOO|BAR|BAZ') })

    ---------------

    transpose

    
    transpose<T>(list: (T[])[]): (T[])[]
    
    const list = [[10, 11], [20], [], [30, 31, 32]]
    const expected = [[10, 20, 30], [11, 31], [32]]
    
    const result = R.transpose(list)
    // => `result` is equal to `expected`
    

    Try this R.transpose example in Rambda REPL

    All Typescript definitions typescript transpose<T>(list: (T[])[]): (T[])[];
    R.transpose source javascript import { _isArray } from './_internals/_isArray.js' export function transpose(array){ return array.reduce((acc, el) => { el.forEach((nestedEl, i) => _isArray(acc[ i ]) ? acc[ i ].push(nestedEl) : acc.push([ nestedEl ])) return acc }, []) }
    Tests javascript import { transpose } from './transpose.js' test('happy', () => { const input = [ [ 'a', 1 ], [ 'b', 2 ], [ 'c', 3 ], ] expect(transpose(input)).toEqual([ [ 'a', 'b', 'c' ], [ 1, 2, 3 ], ]) }) test('when rows are shorter', () => { const actual = transpose([ [ 10, 11 ], [ 20 ], [], [ 30, 31, 32 ] ]) const expected = [ [ 10, 20, 30 ], [ 11, 31 ], [ 32 ] ] expect(actual).toEqual(expected) }) test('with empty array', () => { expect(transpose([])).toEqual([]) }) test('array with falsy values', () => { const actual = transpose([ [ true, false, undefined, null ], [ null, undefined, false, true ], ]) const expected = [ [ true, null ], [ false, undefined ], [ undefined, false ], [ null, true ], ] expect(actual).toEqual(expected) })
    Typescript test typescript import {transpose} from 'rambda' const input = [ ['a', 1], ['b', 2], ['c', 3], ] describe('R.transpose', () => { it('happy', () => { const result = transpose(input) result // $ExpectType (string | number)[][] }) })

    ---------------

    trim

    
    trim(str: string): string
    
    R.trim('  foo  ') 
    // => 'foo'
    

    Try this R.trim example in Rambda REPL

    All Typescript definitions typescript trim(str: string): string;
    R.trim source javascript export function trim(str){ return str.trim() }
    Tests javascript import { trim } from './trim.js' test('trim', () => { expect(trim(' foo ')).toEqual('foo') })

    ---------------

    tryCatch

    It returns function that runs fn in try/catch block. If there was an error, then fallback is used to return the result. Note that fn can be value or asynchronous/synchronous function(unlike Ramda where fallback can only be a synchronous function).

    :boom: Please check the tests of R.tryCatch to fully understand how this method works.

    const fn = x => x.foo
    
    const result = [
      R.tryCatch(fn, false)(null),
      R.tryCatch(fn, false)({foo: 'bar'})
    ]
    // => [false, 'bar']
    

    Try this R.tryCatch example in Rambda REPL

    ---------------

    type

    It accepts any input and it returns its type.

    :boom: NaN, Promise and Async are types specific for Rambda.

    R.type(() => {}) // => 'Function'
    R.type(async () => {}) // => 'Async'
    R.type([]) // => 'Array'
    R.type({}) // => 'Object'
    R.type('foo') // => 'String'
    R.type(1) // => 'Number'
    R.type(true) // => 'Boolean'
    R.type(null) // => 'Null'
    R.type(/[A-z]/) // => 'RegExp'
    R.type('foo'*1) // => 'NaN'
    
    const delay = ms => new Promise(resolve => {
      setTimeout(function () {
        resolve()
      }, ms)
    })
    R.type(delay) // => 'Promise'
    

    Try this R.type example in Rambda REPL

    ---------------

    unapply

    
    unapply<T = any>(fn: (args: any[]) => T): (...args: any[]) => T
    

    It calls a function fn with the list of values of the returned function.

    R.unapply is the opposite of R.apply method.

    R.unapply(JSON.stringify)(1, 2, 3)
    //=> '[1,2,3]'
    

    Try this R.unapply example in Rambda REPL

    All Typescript definitions typescript unapply<T = any>(fn: (args: any[]) => T): (...args: any[]) => T;
    R.unapply source javascript export function unapply(fn){ return function (...args){ return fn.call(this, args) } }
    Tests javascript import { apply } from './apply.js' import { converge } from './converge.js' import { identity } from './identity.js' import { prop } from './prop.js' import { sum } from './sum.js' import { unapply } from './unapply.js' test('happy', () => { const fn = unapply(identity) expect(fn( 1, 2, 3 )).toEqual([ 1, 2, 3 ]) expect(fn()).toEqual([]) }) test('returns a function which is always passed one argument', () => { const fn = unapply(function (){ return arguments.length }) expect(fn('x')).toEqual(1) expect(fn('x', 'y')).toEqual(1) expect(fn( 'x', 'y', 'z' )).toEqual(1) }) test('forwards arguments to decorated function as an array', () => { const fn = unapply(xs => '[' + xs + ']') expect(fn(2)).toEqual('[2]') expect(fn(2, 4)).toEqual('[2,4]') expect(fn( 2, 4, 6 )).toEqual('[2,4,6]') }) test('returns a function with length 0', () => { const fn = unapply(identity) expect(fn.length).toEqual(0) }) test('is the inverse of R.apply', () => { let a, b, c, d, e, f, g, n const rand = function (){ return Math.floor(200 * Math.random()) - 100 } f = Math.max g = unapply(apply(f)) n = 1 while (n <= 100){ a = rand() b = rand() c = rand() d = rand() e = rand() expect(f( a, b, c, d, e )).toEqual(g( a, b, c, d, e )) n += 1 } f = function (xs){ return '[' + xs + ']' } g = apply(unapply(f)) n = 1 while (n <= 100){ a = rand() b = rand() c = rand() d = rand() e = rand() expect(f([ a, b, c, d, e ])).toEqual(g([ a, b, c, d, e ])) n += 1 } }) test('it works with converge', () => { const fn = unapply(sum) const convergeFn = converge(fn, [ prop('a'), prop('b'), prop('c') ]) const obj = { a : 1337, b : 42, c : 1, } const expected = 1337 + 42 + 1 expect(convergeFn(obj)).toEqual(expected) })
    Typescript test typescript import {join, unapply, sum} from 'rambda' describe('R.unapply', () => { it('happy', () => { const fn = unapply(sum) fn(1, 2, 3) // $ExpectType number }) it('joins a string', () => { const fn = unapply(join('')) fn('s', 't', 'r', 'i', 'n', 'g') // $ExpectType string }) })

    ---------------

    union

    
    union<T>(x: T[], y: T[]): T[]
    

    It takes two lists and return a new list containing a merger of both list with removed duplicates.

    R.equals is used to compare for duplication.

    const result = R.union([1,2,3], [3,4,5]);
    // => [1, 2, 3, 4, 5]
    

    Try this R.union example in Rambda REPL

    All Typescript definitions typescript union<T>(x: T[], y: T[]): T[]; union<T>(x: T[]): (y: T[]) => T[];
    R.union source javascript import { cloneList } from './_internals/cloneList.js' import { includes } from './includes.js' export function union(x, y){ if (arguments.length === 1) return _y => union(x, _y) const toReturn = cloneList(x) y.forEach(yInstance => { if (!includes(yInstance, x)) toReturn.push(yInstance) }) return toReturn }
    Tests javascript import { union } from './union.js' test('happy', () => { expect(union([ 1, 2 ], [ 2, 3 ])).toEqual([ 1, 2, 3 ]) }) test('with list of objects', () => { const list1 = [ { a : 1 }, { a : 2 } ] const list2 = [ { a : 2 }, { a : 3 } ] const result = union(list1)(list2) })
    Typescript test typescript import {union} from 'rambda' describe('R.union', () => { it('happy', () => { const result = union([1, 2], [2, 3]) result // $ExpectType number[] }) it('with array of objects - case 1', () => { const list1 = [{a: 1}, {a: 2}] const list2 = [{a: 2}, {a: 3}] const result = union(list1, list2) result // $ExpectType { a: number; }[] }) it('with array of objects - case 2', () => { const list1 = [{a: 1, b: 1}, {a: 2}] const list2 = [{a: 2}, {a: 3, b: 3}] const result = union(list1, list2) result[0].a // $ExpectType number result[0].b // $ExpectType number | undefined }) }) describe('R.union - curried', () => { it('happy', () => { const result = union([1, 2])([2, 3]) result // $ExpectType number[] }) it('with array of objects - case 1', () => { const list1 = [{a: 1}, {a: 2}] const list2 = [{a: 2}, {a: 3}] const result = union(list1)(list2) result // $ExpectType { a: number; }[] }) it('with array of objects - case 2', () => { const list1 = [{a: 1, b: 1}, {a: 2}] const list2 = [{a: 2}, {a: 3, b: 3}] const result = union(list1)(list2) result[0].a // $ExpectType number result[0].b // $ExpectType number | undefined }) })

    ---------------

    uniq

    
    uniq<T>(list: T[]): T[]
    

    It returns a new array containing only one copy of each element of list.

    R.equals is used to determine equality.

    const list = [1, 1, {a: 1}, {a: 2}, {a:1}]
    
    R.uniq(list)
    // => [1, {a: 1}, {a: 2}]
    

    Try this R.uniq example in Rambda REPL

    All Typescript definitions typescript uniq<T>(list: T[]): T[];
    R.uniq source javascript import { _Set } from './_internals/set.js' export function uniq(list){ const set = new _Set() const willReturn = [] list.forEach(item => { if (set.checkUniqueness(item)){ willReturn.push(item) } }) return willReturn }
    Tests javascript import { uniq as uniqRamda } from 'ramda' import { uniq } from './uniq.js' test('happy', () => { const list = [ 1, 2, 3, 3, 3, 1, 2, 0 ] expect(uniq(list)).toEqual([ 1, 2, 3, 0 ]) }) test('with object', () => { const list = [ { a : 1 }, { a : 2 }, { a : 1 }, { a : 2 } ] expect(uniq(list)).toEqual([ { a : 1 }, { a : 2 } ]) }) test('with nested array', () => { expect(uniq([ [ 42 ], [ 42 ] ])).toEqual([ [ 42 ] ]) }) test('with booleans', () => { expect(uniq([ [ false ], [ false ], [ true ] ])).toEqual([ [ false ], [ true ] ]) }) test('with falsy values', () => { expect(uniq([ undefined, null ])).toEqual([ undefined, null ]) }) test('can distinct between string and number', () => { expect(uniq([ 1, '1' ])).toEqual([ 1, '1' ]) })
    Typescript test typescript import {uniq} from 'rambda' describe('R.uniq', () => { it('happy', () => { const result = uniq([1, 2, 3, 3, 3, 1, 2, 0]) result // $ExpectType number[] }) })
    Rambda is faster than Ramda with 86.73% text const R = require('../../dist/rambda.js') const { uniqListOfStrings, uniqListOfBooleans, uniqListOfNumbers, uniqListOfLists, uniqListOfObjects, } = require('./_utils.js') const limit = 100 const modes = [ uniqListOfStrings(limit), uniqListOfBooleans(limit), uniqListOfNumbers(limit), uniqListOfLists(limit), uniqListOfObjects(limit), ] function applyBenchmark(fn, input){ fn(input) } const tests = [ { label : 'Rambda', fn : R.uniq, }, { label : 'Ramda', fn : Ramda.uniq, }, ] tests, modes, applyBenchmark, }

    ---------------

    uniqWith

    
    uniqWith<T, U>(predicate: (x: T, y: T) => boolean, list: T[]): T[]
    

    It returns a new array containing only one copy of each element in list according to predicate function.

    This predicate should return true, if two elements are equal.

    const list = [
      {id: 0, title:'foo'},
      {id: 1, title:'bar'},
      {id: 2, title:'baz'},
      {id: 3, title:'foo'},
      {id: 4, title:'bar'},
    ]
    
    const expected = [
      {id: 0, title:'foo'},
      {id: 1, title:'bar'},
      {id: 2, title:'baz'},
    ]
    
    const predicate = (x,y) => x.title === y.title
    
    const result = R.uniqWith(predicate, list)
    // => `result` is equal to `expected`
    

    Try this R.uniqWith example in Rambda REPL

    All Typescript definitions typescript uniqWith<T, U>(predicate: (x: T, y: T) => boolean, list: T[]): T[]; uniqWith<T, U>(predicate: (x: T, y: T) => boolean): (list: T[]) => T[];
    R.uniqWith source javascript function includesWith( predicate, target, list ){ let willReturn = false let index = -1 while (++index < list.length && !willReturn){ const value = list[ index ] if (predicate(target, value)){ willReturn = true } } return willReturn } export function uniqWith(predicate, list){ if (arguments.length === 1) return _list => uniqWith(predicate, _list) let index = -1 const willReturn = [] while (++index < list.length){ const value = list[ index ] if (!includesWith( predicate, value, willReturn )){ willReturn.push(value) } } return willReturn }
    Tests javascript import { uniqWith as uniqWithRamda } from 'ramda' import { uniqWith } from './uniqWith.js' const list = [ { a : 1 }, { a : 1 } ] test('happy', () => { const fn = (x, y) => x.a === y.a const result = uniqWith(fn, list) expect(result).toEqual([ { a : 1 } ]) }) test('with list of strings', () => { const fn = (x, y) => x.length === y.length const list = [ '0', '11', '222', '33', '4', '55' ] const result = uniqWith(fn)(list) const resultRamda = uniqWithRamda(fn, list) expect(result).toEqual([ '0', '11', '222' ]) expect(resultRamda).toEqual([ '0', '11', '222' ]) })
    Typescript test typescript import {uniqWith} from 'rambda' describe('R.uniqWith', () => { it('happy', () => { const list = [{a: 1}, {a: 1}] const fn = (x: any, y: any) => x.a === y.a const result = uniqWith(fn, list) result // $ExpectType { a: number; }[] }) })
    Rambda is slower than Ramda with 13.67% text const R = require('../../dist/rambda.js') const { uniqListOfStrings, uniqListOfBooleans, uniqListOfNumbers, uniqListOfLists, uniqListOfObjects, } = require('./_utils.js') const limit = 100 const modes = [ [ uniqListOfStrings(limit), (x, y) => x.length === y.length ], [ uniqListOfBooleans(limit), (x, y) => x === y ], [ uniqListOfNumbers(limit), (x, y) => x > y ], [ uniqListOfLists(limit), (x, y) => x.length === y.length ], [ uniqListOfObjects(limit), x => (x, y) => Object.keys(x).length === Object.keys(y).length, ], ] function applyBenchmark(fn, input){ return fn(input[ 1 ], input[ 0 ]) } const tests = [ { label : 'Rambda', fn : R.uniqWith, }, { label : 'Ramda', fn : Ramda.uniqWith, }, ] modes, tests, applyBenchmark, }

    ---------------

    unless

    
    unless<T, U>(predicate: (x: T) => boolean, whenFalseFn: (x: T) => U, x: T): T | U
    

    The method returns function that will be called with argument input.

    If predicate(input) returns false, then the end result will be the outcome of whenFalse(input).

    In the other case, the final output will be the input itself.

    const fn = R.unless(
      x => x > 2,
      x => x + 10
    )
    
    const result = [
      fn(1),
      fn(5)
    ]
    // => [11, 5]
    

    Try this R.unless example in Rambda REPL

    All Typescript definitions typescript unless<T, U>(predicate: (x: T) => boolean, whenFalseFn: (x: T) => U, x: T): T | U; unless<T, U>(predicate: (x: T) => boolean, whenFalseFn: (x: T) => U): (x: T) => T | U; unless<T>(predicate: (x: T) => boolean, whenFalseFn: (x: T) => T, x: T): T; unless<T>(predicate: (x: T) => boolean, whenFalseFn: (x: T) => T): (x: T) => T;
    R.unless source javascript export function unless(predicate, whenFalse){ if (arguments.length === 1){ return _whenFalse => unless(predicate, _whenFalse) } return input => predicate(input) ? input : whenFalse(input) }
    Tests javascript import { inc } from './inc.js' import { isNil } from './isNil.js' import { unless } from './unless.js' test('happy', () => { const safeInc = unless(isNil, inc) expect(safeInc(null)).toBeNull() expect(safeInc(1)).toBe(2) }) test('curried', () => { const safeIncCurried = unless(isNil)(inc) expect(safeIncCurried(null)).toBeNull() })
    Typescript test typescript import {unless, inc} from 'rambda' describe('R.unless', () => { it('happy', () => { const fn = unless(x => x > 5, inc) const result = fn(1) result // $ExpectType number }) it('with one explicit type', () => { const result = unless( x => { x // $ExpectType number return x > 5 }, x => { x // $ExpectType number return x + 1 }, 1 ) result // $ExpectType number }) it('with two different explicit types', () => { const result = unless( x => { x // $ExpectType number return x > 5 }, x => { x // $ExpectType number return `${x}-foo` }, 1 ) result // $ExpectType string | number }) }) describe('R.unless - curried', () => { it('happy', () => { const fn = unless(x => x > 5, inc) const result = fn(1) result // $ExpectType number }) it('with one explicit type', () => { const fn = unless<number>( x => { x // $ExpectType number return x > 5 }, x => { x // $ExpectType number return x + 1 } ) const result = fn(1) result // $ExpectType number }) it('with two different explicit types', () => { const fn = unless<number, string>( x => { x // $ExpectType number return x > 5 }, x => { x // $ExpectType number return `${x}-foo` } ) const result = fn(1) result // $ExpectType string | number }) })

    ---------------

    unwind

    const obj = {
      a: 1,
      b: [2, 3],
    }
    const result = unwind('b', Record<string, unknown>)
    const expected = [{a:1, b:2}, {a:1, b:3}]
    // => `result` is equal to `expected`
    

    Try this R.unwind example in Rambda REPL

    ---------------

    update

    
    update<T>(index: number, newValue: T, list: T[]): T[]
    

    It returns a copy of list with updated element at index with newValue.

    const index = 2
    const newValue = 88
    const list = [1, 2, 3, 4, 5]
    
    const result = R.update(index, newValue, list)
    // => [1, 2, 88, 4, 5]
    

    Try this R.update example in Rambda REPL

    All Typescript definitions typescript update<T>(index: number, newValue: T, list: T[]): T[]; update<T>(index: number, newValue: T): (list: T[]) => T[];
    R.update source javascript import { cloneList } from './_internals/cloneList.js' import { curry } from './curry.js' function updateFn( index, newValue, list ){ const clone = cloneList(list) if (index === -1) return clone.fill(newValue, index) return clone.fill( newValue, index, index + 1 ) } export const update = curry(updateFn)
    Tests javascript import { update } from './update.js' const list = [ 1, 2, 3 ] test('happy', () => { const newValue = 8 const index = 1 const result = update( index, newValue, list ) const curriedResult = update(index, newValue)(list) const tripleCurriedResult = update(index)(newValue)(list) const expected = [ 1, 8, 3 ] expect(result).toEqual(expected) expect(curriedResult).toEqual(expected) expect(tripleCurriedResult).toEqual(expected) }) test('list has no such index', () => { const newValue = 8 const index = 10 const result = update( index, newValue, list ) expect(result).toEqual(list) }) test('with negative index', () => { expect(update( -1, 10, [ 1 ] )).toEqual([ 10 ]) expect(update( -1, 10, [] )).toEqual([]) expect(update( -1, 10, list )).toEqual([ 1, 2, 10 ]) expect(update( -2, 10, list )).toEqual([ 1, 10, 3 ]) expect(update( -3, 10, list )).toEqual([ 10, 2, 3 ]) })
    Typescript test typescript import {update} from 'rambda' describe('R.update', () => { it('happy', () => { const result = update(1, 0, [1, 2, 3]) result // $ExpectType number[] }) })
    Rambda is faster than Ramda with 52.35% text const R = require('../../dist/rambda.js') const list = [ 0, 1, 2 ] const index = 1 const replacer = 7 const update = [ { label : 'Rambda', fn : () => { R.update( replacer, index, list ) R.update(replacer, index)(list) R.update(replacer)(index)(list) }, }, { label : 'Ramda', fn : () => { Ramda.update( replacer, index, list ) Ramda.update(replacer, index)(list) Ramda.update(replacer)(index)(list) }, }, ]

    ---------------

    values

    
    values<T extends object, K extends keyof T>(obj: T): T[K][]
    

    With correct input, this is nothing more than Object.values(Record<string, unknown>). If obj is not an object, then it returns an empty array.

    const obj = {a:1, b:2}
    
    R.values(Record<string, unknown>)
    // => [1, 2]
    

    Try this R.values example in Rambda REPL

    All Typescript definitions typescript values<T extends object, K extends keyof T>(obj: T): T[K][];
    R.values source javascript import { type } from './type.js' export function values(obj){ if (type(obj) !== 'Object') return [] return Object.values(obj) }
    Tests javascript import { values } from './values.js' test('happy', () => { expect(values({ a : 1, b : 2, c : 3, })).toEqual([ 1, 2, 3 ]) }) test('with bad input', () => { expect(values(null)).toEqual([]) expect(values(undefined)).toEqual([]) expect(values(55)).toEqual([]) expect(values('foo')).toEqual([]) expect(values(true)).toEqual([]) expect(values(false)).toEqual([]) expect(values(NaN)).toEqual([]) expect(values(Infinity)).toEqual([]) expect(values([])).toEqual([]) })
    Typescript test typescript import {values} from 'rambda' describe('R.values', () => { it('happy', () => { const result = values({ a: 1, b: 2, c: 3, }) result // $ExpectType number[] }) })

    ---------------

    view

    
    view<T, U>(lens: Lens): (target: T) => U
    

    It returns the value of lens focus over target object.

    const lens = R.lensProp('x')
    
    R.view(lens, {x: 1, y: 2}) // => 1
    R.view(lens, {x: 4, y: 2}) // => 4
    

    Try this R.view example in Rambda REPL

    All Typescript definitions typescript view<T, U>(lens: Lens): (target: T) => U; view<T, U>(lens: Lens, target: T): U;
    R.view source javascript const Const = x => ({ x, map : fn => Const(x), }) export function view(lens, target){ if (arguments.length === 1) return _target => view(lens, _target) return lens(Const)(target).x }
    Tests javascript import { assoc } from './assoc.js' import { lens } from './lens.js' import { prop } from './prop.js' import { view } from './view.js' const testObject = { foo : 'Led Zeppelin' } const assocLens = lens(prop('foo'), assoc('foo')) test('happy', () => { expect(view(assocLens, testObject)).toEqual('Led Zeppelin') })
    Typescript test typescript import {lens, view, assoc} from 'rambda' interface Input { foo: string } const testObject: Input = { foo: 'Led Zeppelin', } const fooLens = lens<Input, string, string>((x: Input) => { return x.foo }, assoc('foo')) describe('R.view', () => { it('happt', () => { const result = view<Input, string>(fooLens, testObject) result // $ExpectType string }) })
    Rambda is faster than Ramda with 76.15% text const R = require('../../dist/rambda.js') const testObj = { a : 1 } const last = [ { label : 'Rambda', fn : () => { R.view(R.lensProp('a'), testObj) }, }, { label : 'Ramda', fn : () => { Ramda.view(Ramda.lensProp('a'), testObj) }, }, ]

    ---------------

    when

    
    when<T, U>(predicate: (x: T) => boolean, whenTrueFn: (a: T) => U, input: T): T | U
    
    All Typescript definitions typescript when<T, U>(predicate: (x: T) => boolean, whenTrueFn: (a: T) => U, input: T): T | U; when<T, U>(predicate: (x: T) => boolean, whenTrueFn: (a: T) => U): (input: T) => T | U; when<T, U>(predicate: (x: T) => boolean): ((whenTrueFn: (a: T) => U) => (input: T) => T | U);
    R.when source javascript import { curry } from './curry.js' function whenFn( predicate, whenTrueFn, input ){ if (!predicate(input)) return input return whenTrueFn(input) } export const when = curry(whenFn)
    Tests javascript import { add } from './add.js' import { when } from './when.js' const predicate = x => typeof x === 'number' test('happy', () => { const fn = when(predicate, add(11)) expect(fn(11)).toBe(22) expect(fn('foo')).toBe('foo') })
    Typescript test typescript import {when} from 'rambda' const predicate = (x: number) => x > 2 const whenTrueFn = (x: number) => String(x) describe('R.when', () => { it('happy', () => { const result = when(predicate, whenTrueFn, 1) result // $ExpectType string | 1 }) it('curry 1', () => { const fn = when(predicate, whenTrueFn) const result = fn(1) result // $ExpectType string | number }) it('curry 2 require explicit types', () => { const fn = when<number, string>(predicate)(whenTrueFn) const result = fn(1) result // $ExpectType string | number }) })

    ---------------

    where

    
    where<T, U>(conditions: T, input: U): boolean
    

    It returns true if all each property in conditions returns true when applied to corresponding property in input object.

    const condition = R.where({
      a : x => typeof x === "string",
      b : x => x === 4
    })
    const input = {
      a : "foo",
      b : 4,
      c : 11,
    }
    
    const result = condition(input) 
    // => true
    

    Try this R.where example in Rambda REPL

    All Typescript definitions typescript where<T, U>(conditions: T, input: U): boolean; where<T>(conditions: T): <U>(input: U) => boolean; where<ObjFunc2, U>(conditions: ObjFunc2, input: U): boolean; where<ObjFunc2>(conditions: ObjFunc2): <U>(input: U) => boolean;
    R.where source javascript export function where(conditions, input){ if (input === undefined){ return _input => where(conditions, _input) } let flag = true for (const prop in conditions){ const result = conditions[ prop ](input[ prop ]) if (flag && result === false){ flag = false } } return flag }
    Tests javascript import {equals} from './equals.js' import {where} from './where.js' test('when true', () => { const predicate = where({ a: equals('foo'), b: equals('bar'), }) expect( predicate({ a: 'foo', b: 'bar', x: 11, y: 19, }) ).toBeTrue() }) test('when false', () => { const predicate = where({ a: equals('foo'), b: equals('baz'), }) expect( predicate({ a: 'foo', b: 'bar', x: 11, y: 19, }) ).toBeFalse() })
    Typescript test typescript import {where, equals} from 'rambda' describe('R.where', () => { it('happy', () => { const input = { a: 'foo', b: 'bar', x: 11, y: 19, } const conditions = { a: equals('foo'), b: equals('bar'), } const result = where(conditions, input) const curriedResult = where(conditions)(input) result // $ExpectType boolean curriedResult // $ExpectType boolean }) })

    ---------------

    whereAny

    Same as R.where, but it will return true if at least one condition check returns true.

    const conditions = {
      a: a => a > 1,
      b: b => b > 2,
    }
    const result = [
      R.whereAny(conditions, {b:3}),
      R.whereAny(conditions, {c:4})
    ]
    // => [true, false]
    

    Try this R.whereAny example in Rambda REPL

    ---------------

    whereEq

    
    whereEq<T, U>(condition: T, input: U): boolean
    

    It will return true if all of input object fully or partially include rule object.

    R.equals is used to determine equality.

    const condition = { a : { b : 1 } }
    const input = {
      a : { b : 1 },
      c : 2
    }
    
    const result = whereEq(condition, input)
    // => true
    

    Try this R.whereEq example in Rambda REPL

    All Typescript definitions typescript whereEq<T, U>(condition: T, input: U): boolean; whereEq<T>(condition: T): <U>(input: U) => boolean;
    R.whereEq source javascript import { equals } from './equals.js' import { filter } from './filter.js' export function whereEq(condition, input){ if (arguments.length === 1){ return _input => whereEq(condition, _input) } const result = filter((conditionValue, conditionProp) => equals(conditionValue, input[ conditionProp ]), condition) return Object.keys(result).length === Object.keys(condition).length }
    Tests javascript import { whereEq } from './whereEq.js' test('when true', () => { const condition = { a : 1 } const input = { a : 1, b : 2, } const result = whereEq(condition, input) const expectedResult = true expect(result).toEqual(expectedResult) }) test('when false', () => { const condition = { a : 1 } const input = { b : 2 } const result = whereEq(condition, input) const expectedResult = false expect(result).toEqual(expectedResult) }) test('with nested object', () => { const condition = { a : { b : 1 } } const input = { a : { b : 1 }, c : 2, } const result = whereEq(condition)(input) const expectedResult = true expect(result).toEqual(expectedResult) }) test('with wrong input', () => { const condition = { a : { b : 1 } } expect(() => whereEq(condition, null)).toThrowWithMessage(TypeError, 'Cannot read properties of null (reading \'a\')') })
    Typescript test typescript import {whereEq} from 'rambda' describe('R.whereEq', () => { it('happy', () => { const result = whereEq({a: {b: 2}}, {b: 2}) const curriedResult = whereEq({a: {b: 2}})({b: 2}) result // $ExpectType boolean curriedResult // $ExpectType boolean }) })

    ---------------

    without

    
    without<T>(matchAgainst: T[], source: T[]): T[]
    

    It will return a new array, based on all members of source list that are not part of matchAgainst list.

    R.equals is used to determine equality.

    const source = [1, 2, 3, 4]
    const matchAgainst = [2, 3]
    
    const result = R.without(matchAgainst, source)
    // => [1, 4]
    

    Try this R.without example in Rambda REPL

    All Typescript definitions typescript without<T>(matchAgainst: T[], source: T[]): T[]; without<T>(matchAgainst: T[]): (source: T[]) => T[];
    R.without source javascript import { _indexOf } from './equals.js' import { reduce } from './reduce.js' export function without(matchAgainst, source){ if (source === undefined){ return _source => without(matchAgainst, _source) } return reduce( (prev, current) => _indexOf(current, matchAgainst) > -1 ? prev : prev.concat(current), [], source ) }
    Tests javascript import { without as withoutRamda } from 'ramda' import { without } from './without.js' test('should return a new list without values in the first argument', () => { const itemsToOmit = [ 'A', 'B', 'C' ] const collection = [ 'A', 'B', 'C', 'D', 'E', 'F' ] expect(without(itemsToOmit, collection)).toEqual([ 'D', 'E', 'F' ]) expect(without(itemsToOmit)(collection)).toEqual([ 'D', 'E', 'F' ]) }) test('with list of objects', () => { const itemsToOmit = [ { a : 1 }, { c : 3 } ] const collection = [ { a : 1 }, { b : 2 }, { c : 3 }, { d : 4 } ] const expected = [ { b : 2 }, { d : 4 } ] expect(without(itemsToOmit, collection)).toEqual(expected) expect(withoutRamda(itemsToOmit, collection)).toEqual(expected) }) test('ramda accepts string as target input while rambda throws', () => { expect(withoutRamda('0:1', [ '0', '0:1' ])).toEqual([]) expect(() => without('0:1', [ '0', '0:1' ])).toThrow() expect(without([ '0:1' ], [ '0', '0:1' ])).toEqual([ '0' ]) }) test('ramda test', () => { expect(without([ 1, 2 ])([ 1, 2, 1, 3, 4 ])).toEqual([ 3, 4 ]) })
    Typescript test typescript import {without} from 'rambda' const itemsToOmit = ['A', 'B', 'C'] const collection = ['A', 'B', 'C', 'D', 'E', 'F'] describe('R.without', () => { it('happy', () => { const result = without(itemsToOmit, collection) result // $ExpectType string[] }) it('curried', () => { const result = without(itemsToOmit)(collection) result // $ExpectType string[] }) })

    ---------------

    xor

    
    xor(x: boolean, y: boolean): boolean
    

    Logical XOR

    const result = [
      xor(true, true),
      xor(false, false),
      xor(false, true),
    ]
    // => [false, false, true]
    

    Try this R.xor example in Rambda REPL

    All Typescript definitions typescript xor(x: boolean, y: boolean): boolean; xor(y: boolean): (y: boolean) => boolean;
    R.xor source javascript export function xor(a, b){ if (arguments.length === 1) return _b => xor(a, _b) return Boolean(a) && !b || Boolean(b) && !a }
    Tests javascript import {xor} from './xor.js' test('compares two values with exclusive or', () => { expect(xor(true, true)).toBeFalse() expect(xor(true, false)).toBeTrue() expect(xor(false, true)).toBeTrue() expect(xor(false, false)).toBeFalse() }) test('when both values are truthy, it should return false', () => { expect(xor(true, 'foo')).toBeFalse() expect(xor(42, true)).toBeFalse() expect(xor('foo', 42)).toBeFalse() expect(xor({}, true)).toBeFalse() expect(xor(true, [])).toBeFalse() expect(xor([], {})).toBeFalse() expect(xor(new Date(), true)).toBeFalse() expect(xor(true, Infinity)).toBeFalse() expect(xor(Infinity, new Date())).toBeFalse() }) test('when both values are falsy, it should return false', () => { expect(xor(null, false)).toBeFalse() expect(xor(false, undefined)).toBeFalse() expect(xor(undefined, null)).toBeFalse() expect(xor(0, false)).toBeFalse() expect(xor(false, NaN)).toBeFalse() expect(xor(NaN, 0)).toBeFalse() expect(xor('', false)).toBeFalse() }) test('when one argument is truthy and the other is falsy, it should return true', () => { expect(xor('foo', null)).toBeTrue() expect(xor(null, 'foo')).toBeTrue() expect(xor(undefined, 42)).toBeTrue() expect(xor(42, undefined)).toBeTrue() expect(xor(Infinity, NaN)).toBeTrue() expect(xor(NaN, Infinity)).toBeTrue() expect(xor({}, '')).toBeTrue() expect(xor('', {})).toBeTrue() expect(xor(new Date(), 0)).toBeTrue() expect(xor(0, new Date())).toBeTrue() expect(xor([], null)).toBeTrue() expect(xor(undefined, [])).toBeTrue() })
    Typescript test typescript import {xor} from 'rambda' describe('R.xor', () => { it('happy', () => { xor(true, false) // $ExpectType boolean }) it('curry', () => { xor(true)(false) // $ExpectType boolean }) })

    ---------------

    zip

    
    zip<K, V>(x: K[], y: V[]): KeyValuePair<K, V>[]
    

    It will return a new array containing tuples of equally positions items from both x and y lists.

    The returned list will be truncated to match the length of the shortest supplied list.

    const x = [1, 2]
    const y = ['A', 'B']
    R.zip(x, y)
    // => [[1, 'A'], [2, 'B']]
    
    // truncates to shortest list
    R.zip([...x, 3], ['A', 'B'])
    // => [[1, 'A'], [2, 'B']]
    

    Try this R.zip example in Rambda REPL

    All Typescript definitions typescript zip<K, V>(x: K[], y: V[]): KeyValuePair<K, V>[]; zip<K>(x: K[]): <V>(y: V[]) => KeyValuePair<K, V>[];
    R.zip source javascript export function zip(left, right){ if (arguments.length === 1) return _right => zip(left, _right) const result = [] const length = Math.min(left.length, right.length) for (let i = 0; i < length; i++){ result[ i ] = [ left[ i ], right[ i ] ] } return result }
    Tests javascript import { zip } from './zip.js' const array1 = [ 1, 2, 3 ] const array2 = [ 'A', 'B', 'C' ] test('should return an array', () => { const actual = zip(array1)(array2) expect(actual).toBeInstanceOf(Array) }) test('should return and array or tuples', () => { const expected = [ [ 1, 'A' ], [ 2, 'B' ], [ 3, 'C' ], ] const actual = zip(array1, array2) expect(actual).toEqual(expected) }) test('should truncate result to length of shorted input list', () => { const expectedA = [ [ 1, 'A' ], [ 2, 'B' ], ] const actualA = zip([ 1, 2 ], array2) expect(actualA).toEqual(expectedA) const expectedB = [ [ 1, 'A' ], [ 2, 'B' ], ] const actualB = zip(array1, [ 'A', 'B' ]) expect(actualB).toEqual(expectedB) })
    Typescript test typescript import {zip} from 'rambda' describe('R.zip', () => { it('happy', () => { const array1 = [1, 2, 3] const array2 = ['A', 'B', 'C'] const result = zip(array1)(array2) result // $ExpectType KeyValuePair<number, string>[] }) })

    ---------------

    zipObj

    
    zipObj<T, K extends string>(keys: K[], values: T[]): { [P in K]: T }
    

    It will return a new object with keys of keys array and values of values array.

    const keys = ['a', 'b', 'c']
    
    R.zipObj(keys, [1, 2, 3])
    // => {a: 1, b: 2, c: 3}
    
    // truncates to shortest list
    R.zipObj(keys, [1, 2])
    // => {a: 1, b: 2}
    

    Try this R.zipObj example in Rambda REPL

    All Typescript definitions typescript zipObj<T, K extends string>(keys: K[], values: T[]): { [P in K]: T }; zipObj<K extends string>(keys: K[]): <T>(values: T[]) => { [P in K]: T }; zipObj<T, K extends number>(keys: K[], values: T[]): { [P in K]: T }; zipObj<K extends number>(keys: K[]): <T>(values: T[]) => { [P in K]: T };
    R.zipObj source javascript import { take } from './take.js' export function zipObj(keys, values){ if (arguments.length === 1) return yHolder => zipObj(keys, yHolder) return take(values.length, keys).reduce(( prev, xInstance, i ) => { prev[ xInstance ] = values[ i ] return prev }, {}) }
    Tests javascript import { equals } from './equals.js' import { zipObj } from './zipObj.js' test('zipObj', () => { expect(zipObj([ 'a', 'b', 'c' ], [ 1, 2, 3 ])).toEqual({ a : 1, b : 2, c : 3, }) }) test('0', () => { expect(zipObj([ 'a', 'b' ])([ 1, 2, 3 ])).toEqual({ a : 1, b : 2, }) }) test('1', () => { expect(zipObj([ 'a', 'b', 'c' ])([ 1, 2 ])).toEqual({ a : 1, b : 2, }) }) test('ignore extra keys', () => { const result = zipObj([ 'a', 'b', 'c', 'd', 'e', 'f' ], [ 1, 2, 3 ]) const expected = { a : 1, b : 2, c : 3, } expect(equals(result, expected)).toBeTrue() })
    Typescript test typescript import {zipObj} from 'rambda' describe('R.zipObj', () => { it('happy', () => { // this is wrong since 24.10.2020 `@types/ramda` changes const result = zipObj(['a', 'b', 'c', 'd'], [1, 2, 3]) result // $ExpectType { b: number; a: number; c: number; d: number; } }) it('imported from @types/ramda', () => { const result = zipObj(['a', 'b', 'c'], [1, 2, 3]) const curriedResult = zipObj(['a', 'b', 'c'])([1, 2, 3]) result // $ExpectType { b: number; a: number; c: number; } curriedResult // $ExpectType { b: number; a: number; c: number; } }) })

    ---------------

    zipWith

    
    zipWith<T, U, TResult>(fn: (x: T, y: U) => TResult, list1: T[], list2: U[]): TResult[]
    
    const list1 = [ 10, 20, 30, 40 ]
    const list2 = [ 100, 200 ]
    
    const result = R.zipWith(
      R.add, list1, list2
    )
    // => [110, 220]
    

    Try this R.zipWith example in Rambda REPL

    All Typescript definitions typescript zipWith<T, U, TResult>(fn: (x: T, y: U) => TResult, list1: T[], list2: U[]): TResult[]; zipWith<T, U, TResult>(fn: (x: T, y: U) => TResult, list1: T[]): (list2: U[]) => TResult[]; zipWith<T, U, TResult>(fn: (x: T, y: U) => TResult): (list1: T[], list2: U[]) => TResult[];
    R.zipWith source javascript import { curry } from './curry.js' import { take } from './take.js' function zipWithFn( fn, x, y ){ return take(x.length > y.length ? y.length : x.length, x).map((xInstance, i) => fn(xInstance, y[ i ])) } export const zipWith = curry(zipWithFn)
    Tests javascript import { add } from './add.js' import { zipWith } from './zipWith.js' const list1 = [ 1, 2, 3 ] const list2 = [ 10, 20, 30, 40 ] const list3 = [ 100, 200 ] test('when second list is shorter', () => { const result = zipWith( add, list1, list3 ) expect(result).toEqual([ 101, 202 ]) }) test('when second list is longer', () => { const result = zipWith( add, list1, list2 ) expect(result).toEqual([ 11, 22, 33 ]) })
    Typescript test typescript import {zipWith} from 'rambda' const list1 = [1, 2] const list2 = [10, 20, 30] describe('R.zipWith', () => { it('happy', () => { const result = zipWith( (x, y) => { x // $ExpectType number y // $ExpectType number return `${x}-${y}` }, list1, list2 ) result // $ExpectType string[] }) it('curried', () => { const result = zipWith((x, y) => { x // $ExpectType unknown y // $ExpectType unknown return `${x}-${y}` })(list1, list2) result // $ExpectType string[] }) })

    ---------------

    ❯ CHANGELOG

    7.1.4

    R.mergeRight not found on Deno import - Issue #633

    7.1.0

    • Add R.mergeRight - introduced by Ramda's latest release. While Ramda renames R.merge, Rambda will keep R.merge.

    • Rambda's pipe/compose doesn't return proper length of composed function which leads to issue with R.applySpec. It was fixed by using Ramda's pipe/compose logic - Issue #627

    • Replace Async with Promise as return type of R.type.

    • Add new types as Typescript output for R.type - "Map", "WeakMap", "Generator", "GeneratorFunction", "BigInt", "ArrayBuffer"

    • Add R.juxt method

    • Add R.propSatisfies method

    • Add new methods after Ramda version upgrade to 0.28.0:

    -- R.count -- R.modifyPath -- R.on -- R.whereAny -- R.partialObject

    7.0.3

    Rambda.none has wrong logic introduced in version 7.0.0 - Issue #625

    7.0.2

    Rambda doesn't work with pnpm due to wrong export configuration - Issue #619

    7.0.1

    • Wrong ESM export configuration in package.json - Issue #614

    7.0.0

    • Braking change - sync R.compose/R.pipe with @types/ramda. That is significant change so as safeguard, it will lead a major bump. Important - this lead to raising required Typescript version to 4.2.2. In other words, to use Rambda you'll need Typescript version 4.2.2 or newer.

    Related commit in @types/ramda - https://github.com/DefinitelyTyped/DefinitelyTyped/commit/286eff4f76d41eb8f091e7437eabd8a60d97fc1f#diff-4f74803fa83a81e47cb17a7d8a4e46a7e451f4d9e5ce2f1bd7a70a72d91f4bc1

    There are several other changes in @types/ramda as stated in this comment. This leads to change of typings for the following methods in Rambda:

    -- R.unless

    -- R.toString

    -- R.ifElse

    -- R.always

    -- R.complement

    -- R.cond

    -- R.is

    -- R.sortBy

    -- R.dissoc

    -- R.toPairs

    -- R.assoc

    -- R.toLower

    -- R.toUpper

    • One more reason for the braking change is changing of export declarations in package.json based on this blog post and this merged Ramda's PR. This also led to renaming of babel.config.js to babel.config.cjs.

    • Add R.apply, R.bind and R.unapply

    • R.startsWith/R.endsWith now support lists as inputs. This way, it matches current Ramda behavior.

    • Remove unused typing for R.chain.

    • R.map/R.filter no longer accept bad inputs as iterable. This way, Rambda behaves more like Ramda, which also throws.

    • Make R.lastIndexOf follow the logic of R.indexOf.

    • Change R.type logic to Ramda logic. This way, R.type can return Error and Set as results.

    • Add missing logic in R.equals to compare sets - Issue #599

    • Improve list cloning - Issue #595

    • Handle multiple inputs with R.allPass and R.anyPass - Issue #604

    • Fix R.length wrong logic with inputs as {length: 123} - Issue #606.

    • Improve non-curry typings of R.merge by using types from mobily/ts-belt.

    • Improve performance of R.uniqWith.

    • Wrong R.update if index is -1 - PR #593

    • Make R.eqProps safe for falsy inputs - based on this opened Ramda PR.

    • Incorrect benchmarks for R.pipe/R.compose - Issue #608

    • Fix R.last/R.head typings - Issue #609

    6.9.0

    Fixing R.uniq was done by improving R.indexOf which has performance implication to all methods importing R.indexOf:

    • R.includes
    • R.intersection
    • R.difference
    • R.excludes
    • R.symmetricDifference
    • R.union

    • R.without no longer support the following case - without('0:1', ['0', '0:1']) // => ['0']. Now it throws as the first argument should be a list, not a string. Ramda, on the other hand, returns an empty list - https://github.com/ramda/ramda/issues/3086.

    6.8.3

    • Fix Typescript build process with rambda/immutable - Issue #572

    • Add R.objOf method

    • Add R.mapObjIndexed method

    • Publish shorter README.md version to NPM

    6.8.0

    • R.has use Object.prototype.hasOwnProperty- Issue #572

    • Expose immutable.ts typings which are Rambda typings with readonly statements - Issue #565

    • Fix R.intersection wrong order compared to Ramda.

    • R.path wrong return of null instead of undefined when path value is null - PR #577

    6.7.0

    • Remove ts-toolbelt types from Typescript definitions. Most affected are the following methods, which lose one of its curried definitions:

    • R.maxBy

    • R.minBy
    • R.pathEq
    • R.viewOr
    • R.when
    • R.merge
    • R.mergeDeepRight
    • R.mergeLeft

    6.6.0

    • Change R.piped typings to mimic that of R.pipe. Main difference is that R.pipe is focused on unary functions.

    • Fix wrong logic when R.without use R.includes while it should use array version of R.includes.

    • Use uglify plugin for UMD bundle.

    • Remove dist folder from .gitignore in order to fix Deno broken package. Issue #570

    • Improve R.fromPairs typings - Issue #567

    6.5.3

    • Wrong logic where R.without use R.includes while it should use the array version of R.includes

    This is Ramda bug, that Rambda also has before this release - https://github.com/ramda/ramda/issues/3086

    6.5.2

    • Wrong R.defaultTo typings - changes introduced in v6.5.0 are missing their TS equivalent.

    • Update dependencies

    6.5.1

    Fix wrong versions in changelog

    6.5.0

    • R.defaultTo no longer accepts infinite inputs, thus it follows Ramda implementation.

    • R.equals supports equality of functions.

    • R.pipe doesn't use R.compose.

    • Close Issue #561 - export several internal TS interfaces and types

    • Close Issue #559 - improve R.propOr typings

    • Add CHANGELOG.md file in release files list

    6.4.0

    • Close Issue #560 - apply immutable lint to Typescript definitions

    • Close Issue #553 - fix problem with curried typings of R.prop

    • Fix wrong R.last typing

    • Upgrade all rollup related dependencies

    • R.type supports Symbol just like Ramda.

    • Remove file extension in main property in package.json in order to allow experimental-modules. See also this Ramda's PR - https://github.com/ramda/ramda/pull/2678/files

    • Import R.indexBy/R.when/R.zipObj/R.propEq/R.complement changes from recent @types/ramda release.

    • R.tryCatch stop supporting asynchronous functions; the previous behaviour is exported to Rambdax as R.tryCatchAsync

    6.3.1

    • Fix missing Evolved declaration in Typescript definition

    6.3.0

    • Add R.takeLastWhile

    • Add R.dropWhile

    • Add R.eqProps

    • Add R.dropLastWhile

    • Add R.dropRepeats

    • Add R.dropRepeatsWith

    • Add R.evolve

    • Add typings for R.takeWhile when iterable is a string

    6.2.0

    • Add R.props

    • Add R.zipWith

    • Add R.splitAt

    • Add R.splitWhen

    • Close Issue #547 - restore readonly declaration in Typescript definitions.

    • R.append/R.prepend now work only with arrays just like Ramda. Previous behaviour was for them to work with both arrays and strings.

    • Sync R.pluck typings with @types/ramda as there was a tiny difference.

    6.1.0

    • Fix R.and wrong definition, because the function doesn't convert the result to boolean. This introduce another difference with @types/ramda.

    • Add R.once

    • Add R.or

    6.0.1

    • Fix typing of R.reject as it wrongly declares that with object, it pass property to predicate.

    6.0.0

    • Breaking change - R.map/R.filter/R.reject/R.forEach/R.partition doesn't pass index as second argument to the predicate, when looping over arrays. The old behaviour of map, filter and forEach can be found in Rambdax methods R.mapIndexed, R.filterIndexed and R.forEachIndexed.

    • Breaking change - R.all/R.none/R.any/R.find/R.findLast/R.findIndex/R.findLastIndex doesn't pass index as second argument to the predicate.

    • Change R.assocPath typings so the user can explicitly sets type of the new object

    • Typings of R.assoc match its @types/ramda counterpart.

    • Simplify R.forEach typings

    • Remove ReadonlyArray<T> pattern from Typescript definitions - not enough value for the noise it adds.

    5.13.1

    • Fix wrong R.takeWhile

    5.13.0

    • Add R.takeWhile method

    • Fix R.lensPath issue when using string as path input. The issue was introduced when fixing Issue #524 in the previous release.

    5.12.1

    • Close Issue #524 - wrong R.assocPath when path includes numbers

    • R.includes throws on wrong input, i.e. R.includes(1, null)

    5.12.0

    • Add R.move method

    • Add R.union method

    • Close Issue #519 - ts-toolbelt needs other type of export with --isolatedModules flag

    • Change R.when implementation and typings to match those of Ramda

    • R.over and R.set use R.curry instead of manual currying

    • R.lensPath typings support string as path, i.e. 'a.b' instead of ['a', 'b']

    • R.equals now supports negative zero just like Ramda.equals

    • R.replace uses R.curry

    5.11.0

    Forgot to export R.of because of wrong marker in files/index.d.ts

    5.10.0

    Close Issue #514 - wrong R.length with empty string

    Close Issue #511 - error in ts-toolbelt library

    Close Issue #510 - R.clamp should throw if min argument is greater than max argument

    • PR #508 - add R.of

    • Definition of R.curry are not same as those of @types/ramda

    • Definitions of R.either is same as that of R.both

    • Definitions of R.ifElse no longer use any type

    • Definition of R.flatten requires passing type for the output

    • Fix definition of R.propOr, R.dissoc

    • Fix curried definitions of R.take, R.takeLast, R.drop and R.dropLast

    • 5.9.0

    • R.pickAll definition allows passing string as path to search.

    • R.propEq definition is now similar to that in @types/ramda.

    • R.none matches R.all implementation and pass index as second argument to predicate input.

    • R.reduce - drop support for object as iterable. Now it throws the same error as Ramda. Also instead of returning the initial value when iterable is undefined, now it throws.

    Add index as additional argument to the Typescript definitions of the following methods:

    • R.all
    • R.find
    • R.findLast
    • R.findIndex
    • R.findLastIndex

    • 5.8.0

    Add R.mergeAll Add R.mergeDeepRight Add R.mergeLeft Add R.partition Add R.pathEq Add R.tryCatch Add R.unless Add R.whereEq Add R.where

    • Add R.last typing for empty array

    • 5.7.0 Revert PR #469 as R.curry was slow | Also now R.flip throws if arity is greater than or equal to 5

    • 5.6.3 Merge several PRs of @farwayer

    • PR #482 - improve R.forEach performance by not using R.map

    • PR #485 - improve R.map performance

    • PR #482 - improve R.reduce performance

    • Fix missing high arity typings for R.compose/pipe

    • R.merge definitions match those of @types/ramda

    • Remove dist folder from Rambda repo

    • 5.6.2

    Close Issue #476 - typesafe R.propEq definitions

    Approve PR #477 - fix R.groupWith when list length is 1

    • 5.6.1

    Update ts-toolbelt files as now there is update pipeline for it.

    Approve PR #474 - intruduce internal isArray helper

    • 5.6.0

    Approve PR #469 - R.flip supports any arity | implement R.curry with R.curryN add R.applySpec

    • 5.5.0

    Close Issue #464 - R.flip should handle functions with arity above 2

    Close Issue #468 - fs-extra should be dev dependency as it was wrongly added as production dependency in 5.2.0

    R.flip typings now match @types/ramda typings

    Add R.hasPath method

    Add R.mathMod typings

    • 5.4.3

    Fix R.omit typings

    • 5.4.2

    Fix R.pick typings

    Close Issue #460 - R.paths should be curried

    • 5.4.1

    Close Issue #458 - wrong R.propIs typing

    • 5.4.0

    Close Issue #408 - add R.chain

    • 5.3.0

    Close Issue #430 - add R.when

    Also restore R.converge, R.findLast, R.findLastIndex and R.curryN as I have forgotten to export them when releasing 5.2.0.

    • 5.2.1

    Fix Typescript comment for every method

    • 5.2.0

    Release new documentation site

    Ramda repo now holds all Rambdax methods and tests

    • 5.1.1

    Add R.converge and R.curryN from PR #412

    Close Issue #410 - wrong implementation of R.groupWith

    Close Issue #411 - change the order of declared R.map typings rules

    • 5.0.0

    Move R.partialCurry to Rambdax(reason for major bump).

    Use new type of export in Typescript definitions.

    Approve PR #381 - add R.applySpec

    • 4.6.0

    Approve PR #375 - add lenses(Thank you @synthet1c)

    Add R.lens

    Add R.lensIndex

    Add R.lensPath

    Add R.lensProp

    Add R.over

    Add R.set

    Add R.view

    Sync with Ramda 0.27

    Add R.paths

    Add R.xor

    Close Issue #373

    Add R.cond

    • 4.5.0 Add R.clamp

    • 4.4.2 Improve R.propOr typings

    • 4.4.1 Make R.reject has the same typing as R.filter

    • 4.4.0 Several changes:

    Close Issue #317 - add R.transpose

    Close Issue #325 - R.filter should return equal values for bad inputs null and undefined

    Approve suggestion for R.indexBy to accept string not only function as first argument.

    Edit of R.path typings

    • 4.2.0 Approve PR #314 - add R.and

    • 4.1.1 Add missing typings for R.slice

    • 4.1.0 Add R.findLast and R.findLastIndex

    • 4.0.2 Fix R.isEmpty wrong behaviour compared to the Ramda method

    • 4.0.1 Approve PR #289 - remove console.log in R.values method

    • 4.0.0 Multiple breaking changes as Rambda methods are changed in order to increase the similarity between with Ramda

    Add to Differences:

    R.type can return 'NaN'
    
    R.compose doesn't pass `this` context
    
    R.clone doesn't work with number, booleans and strings as input
    

    All breaking changes:

    -- R.add works only with numbers

    -- Fix R.adjust which had wrong order of arguments

    -- R.adjust works when index is out of bounds

    -- R.complement support function with multiple arguments

    -- R.compose/pipe throws when called with no argument

    -- R.clone works with Date value as input

    -- R.drop/dropLast/take/takeLast always return new copy of the list/string

    -- R.take/takeLast return original list/string with negative index

    -- R.equals handles NaN and RegExp types

    -- R.type/R.equals supports new Boolean/new Number/new Date/new String expressions

    -- R.has works with non-object

    -- R.ifElse pass all arguments

    -- R.length works with bad input

    -- R.propEq work with bad input for object argument

    -- R.range work with bad inputs

    -- R.times work with bad inputs

    -- R.reverse works with strings

    -- R.splitEvery throws on non-positive integer index

    -- R.test throws just like Ramda when first argument is not regex

    -- R.values works with bad inputs

    -- R.zipObj ignores extra keys

    • 3.3.0

    This is pre 4.0.0 release and it contains all of the above changes

    Close issue #287 - ts-toolbelt directory was changed but not reflected in files property in package.json

    • 3.2.5

    Close issue #273 - ts-toolbelt needs other type of export when isolatedModules TypeScript property

    Close issue #245 - complete typings tests for methods that have more specific Typescript definitions

    • 3.2.1 Fast fix for issue #273 - messed up typings

    • 3.2.0 There are several changes:

    Close issue #263 - broken curry typing solved by ts-toolbelt local dependency.

    Add R.partialCurry typings.

    Approve PR #266 that adds R.slice method.

    • 3.1.0 This might be breaking change for Typescript users, as very different definitions are introduced. With the previous state of the definitions, it was not possible to pass dtslint typings tests.

    • R.either and R.both supports multiple arguments as they should.

    • Several methods added by @squidfunk - R.assocPath, R.symmetricDifference, R.intersperse, R.intersection and R.difference

    • 3.0.1 Close issue #234 - wrong curry typing

    • 3.0.0 Deprecate R.contains, while R.includes is now following Ramda API(it uses R.equals for comparision)

    • 2.14.5 R.without needs currying

    • 2.14.4 Close issue #227 - add index as third argument of R.reduce typings

    • 2.14.2 Use R.curry with R.reduce as manual curry there didn't work as expected.

    • 2.14.1 Fix wrong typescript with R.head - PR #228 pushed by @tonivj5

    • 2.14.0 Add R.groupWith by @selfrefactor | Add R.propOr, R.mathMod, R.mean, R.median, R.negate, R.product by @ku8ar

    • 2.13.0 Add R.identical - PR #217 pushed by @ku8ar

    • 2.12.0 Add R.propIs - PR #213 and add R.sum - issue #207

    • 2.11.2 Close Rambdax issue #32 - wrong R.type when function is input

    • 2.11.1 Approve PR #182 - Changed typings to allow object as input to R.forEach and R.map

    • 2.11.0 Approve PR #179 - R.adjust handles negative index; R.all doesn't need R.filter

    • 2.10.2 Close issue #175 - missing typescript file

    • 2.10.0 Approve huge and important PR #171 submitted by @helmuthdu - Add comments to each method, improve Typescript support

    • 2.9.0 R.toPairs and R.fromPairs

    • 2.8.0 Approve PR #165 R.clone

    • 2.7.1 expose src | Discussed at issue #147

    • 2.7.0 Approve PR #161 R.isEmpty

    • 2.6.0 R.map, R.filter and R.forEach pass original object to iterator as third argument | Discussed at issue #147

    • 2.5.0 Close issue #149 Add R.partial | R.type handles NaN

    • 2.4.0 Major bump of Rollup; Stop building for ES5

    • 2.3.1 Close issue #90 | Add string type of path in R.pathOr

    • 2.3.0 Close issue #89 | Fix missing Number TS definition in R.type

    • 2.2.0 R.defaultTo accepts indefinite number of input arguments. So the following is valid expression: const x = defaultTo('foo',null, null, 'bar')

    • 2.1.0 Restore R.zip using WatermelonDB implementation.

    • 2.0.0 Major version caused by removing of R.zip and R.addIndex. Issue #85 rightfully finds that the implementation of R.addIndex is not correct. This led to removing this method and also of R.zip as it had depended on it. The second change is that R.map, R.filter are passing array index as second argument when looping over arrays. The third change is that R.includes will return false if input is neigher string nor array. The previous behaviour was to throw an error. The last change is to increase the number of methods that are passing index as second argument to the predicate function.

    • 1.2.6 Use src folder instead of modules

    • 1.2.5 Fix omit typing
    • 1.2.4 Add missing Typescript definitions - PR#82
    • 1.2.2 Change curry method used across most of library methods
    • 1.2.1 Add R.assoc | fix passing undefined to R.map and R.merge issue #77
    • 1.2.0 Add R.min, R.minBy, R.max, R.maxBy, R.nth and R.keys
    • 1.1.5 Close issue #74 R.zipObj
    • 1.1.4 Close issue #71 CRA fail to build rambda
    • 1.1.3 Approve PR #70 implement R.groupBy | Close issue #69
    • 1.1.2 Approve PR #67 use babel-plugin-annotate-pure-calls
    • 1.1.1 Approve PR #66 R.zip
    • 1.1.0 R.compose accepts more than one input argument issue #65
    • 1.0.13 Approve PR #64 R.indexOf
    • 1.0.12 Close issue #61 make all functions modules
    • 1.0.11 Close issue #60 problem with babelrc
    • 1.0.10 Close issue #59 add R.dissoc
    • 1.0.9 Close issue #58 - Incorrect R.equals
    • 1.0.8 R.map and R.filter pass object properties when mapping over objects
    • 1.0.7 Add R.uniqWith
    • 1.0.6 Close issue #52 - ES5 compatible code
    • 1.0.5 Close issue #51
    • 1.0.4 Close issue #50 - add R.pipe typings
    • 1.0.3 R.ifElse accept also boolean as condition argument
    • 1.0.2 Remove typedDefaultTo and typedPathOr | Add R.pickAll and R.none
    • 1.0.0 Major change as build is now ES6 not ES5 compatible (Related to issue #46)| Making Rambda fully tree-shakeable| Edit Typescript definition
    • 0.9.8 Revert to ES5 compatible build - issue #46
    • 0.9.7 Refactor for Rollup tree-shake | Remove R.padEnd and R.padStart
    • 0.9.6 Close issue #44 - R.reverse mutates the array
    • 0.9.5 Close issue #45 - invalid Typescript typings
    • 0.9.4 Add R.reject and R.without (PR#41 PR#42) | Remove 'browser' field in package.json due to Webpack bug 4674
    • 0.9.3 Add R.forEach and R.times
    • 0.9.2 Add Typescript definitions
    • 0.9.1 Close issue #36 - move current behaviour of defaultTo to a new method typedDefaultTo; make defaultTo follow Ramda spec; add pathOr; add typedPathOr.
    • 0.9.0 Add R.pipe PR#35
    • 0.8.9 Add R.isNil
    • 0.8.8 Migrate to ES modules PR33 | Add R.flip to the API | R.map/filter works with objects
    • 0.8.7 Change Webpack with Rollup - PR29
    • 0.8.6 Add R.tap and R.identity
    • 0.8.5 Add R.all, R.allPass, R.both, R.either and R.complement
    • 0.8.4 Learning to run yarn test before yarn publish the hard way
    • 0.8.3 Add R.always, R.T and R.F
    • 0.8.2 Add concat, padStart, padEnd, lastIndexOf, toString, reverse, endsWith and startsWith methods
    • 0.8.1 Add R.ifElse
    • 0.8.0 Add R.not, R.includes | Take string as condition for R.pick and R.omit
    • 0.7.6 Fix incorrect implementation of R.values
    • 0.7.5 Fix incorrect implementation of R.omit
    • 0.7.4 issue #13 - Fix R.curry, which used to return incorrectly function when called with more arguments
    • 0.7.3 Close issue #9 - Compile to es2015; Approve PR #10 - add R.addIndex to the API
    • 0.7.2 Add Promise support for R.type
    • 0.7.1 Close issue #7 - add R.reduce to the API
    • 0.7.0 Close issue #5 - change name of curry to partialCurry; add new method curry, which works just like Ramda's curry
    • 0.6.2 Add separate documentation site via docsify

    ---------------

    ❯ Additional info

    Most influential contributors

    • @farwayer - improving performance in R.find, R.filter; give the idea how to make benchmarks more reliable;

    • @thejohnfreeman - add R.assoc, R.chain;

    • @helmuthdu - add R.clone; help improve code style;

    • @jpgorman - add R.zip, R.reject, R.without, R.addIndex;

    • @ku8ar - add R.slice, R.propOr, R.identical, R.propIs and several math related methods; introduce the idea to display missing Ramda methods;

    • @romgrk - add R.groupBy, R.indexBy, R.findLast, R.findLastIndex;

    • @squidfunk - add R.assocPath, R.symmetricDifference, R.difference, R.intersperse;

    • @synthet1c - add all lenses methods; add R.applySpec, R.converge;

    • @vlad-zhukov - help with configuring Rollup, Babel; change export file to use ES module exports;

    Rambda references

    Links to Rambda

    Deprecated from Used by section

    Releases

    Rambda's releases before 6.4.0 were used mostly for testing purposes.

    ---------------

    My other libraries

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