ES2015 template literal tag for i18n and l10n (translation and internationalization)
Filed under miscellaneous

i18n Tagged Template Literals

Overview
Features
Compatibility
Examples
Installation
Usage
Translations as CommonJS Modules
Tools
- Build time translation
- JSON Schema
Credits
License

Overview

This template literal tag adds support for i18n and l10n (translation and internationalization) to your JavaScript project. It provides the following benefits:

Very small footprint
Powerful ES2015 standard template literal syntax
Internationalization based on ECMA-402 standard Intl browser API
JSON Schema powered translations
Tools that can be integrated into your build pipeline and IDE

Features

Translate and internationalize your JavaScript project
Translate your JavaScript library at buildtime
Generate a schema of all i18n tagged template literals in your project for easy JSON based translations
Export translations as CommonJS modules
Validate translations and track translation coverage of your project

Compatibility

This library is using the ECMAScript Internationalization API. ES Internationalization API is implemented in all modern Browsers. For node.js projects you can use Andy Earnshaw's excellent Intl.js polyfill [#34]:

Examples

Installation

$ npm install es2015-i18n-tag --save

Usage

This library is available as CommonJS module and as UMD module that is consumable in CommonJS, AMD and with script tags. The UMD module can be used in environments that don't support CommonJS modules. It is highly recommended to use es2015-i18n-tag as CommonJS module with babel and webpack or browserify. In a Node.js environment you have to use the Intl Polyfill to add support for additional locales [#34].

UMD module on unpkg.com

https://unpkg.com/es2015-i18n-tag/dist/lib/index.umd.min.js

Import and Configuration

import i18n, { i18nConfig }  from 'es2015-i18n-tag'

i18nConfig({
    locales: 'de-DE',    
    group: 'my-lib', // Optional, can be used to avoid configuration overrides. This is recommended for libraries!
    translations: {
        "Hello ${0}, you have ${1} in your bank account.": "Hallo ${0}, Sie haben ${1} auf Ihrem Bankkonto."
    },
    number: {      
        [...options] // Intl NumberFormat options as described here: https://goo.gl/pDwbG2
    },
    date: {
        [...options] // Intl DateTimeFormat options as described here: https://goo.gl/lslekB
    }
})

const name = 'Steffen'
const amount = 1250.33

console.log(i18n`Hello ${ name }, you have ${ amount }:c in your bank account.`)
// Hallo Steffen, Sie haben US$ 1,250.33 auf Ihrem Bankkonto.

Currency formatting

i18nConfig({
    number: { 
        currency: 'EUR'
    }
})

console.log(i18n`Hello ${ name }, you have ${ amount }:c in your bank account.`)
// Hallo Steffen, Sie haben € 1,250.33 auf Ihrem Bankkonto.

console.log(i18n`Hello ${ name }, you have ${ amount }:c(USD) in your bank account.`)
// Hallo Steffen, Sie haben US$ 1,250.33 auf Ihrem Bankkonto.

Date formatting

i18nConfig({
    locales: 'en-US',
    date: { 
        hour12: false 
    }
})

console.log(i18n`Hello ${name}, the date is ${new Date(2012, 11, 20, 19, 0, 0)}:t.`)
// Hello Steffen, the date is 12/20/2012, 19:00:00.

Standard format strings

const date = new Date(2012, 11, 20, 19, 0, 0);

i18n`The date is ${date}:t(D).`

// The date is Thursday, December 20, 2012.

The following standard format strings can be applied to a template expression of type Date:

Format specifier	Description	Examples
"d"	Short date pattern	12/20/2012
"D"	Long date pattern	Thursday, December 20, 2012
"f"	Full date/time pattern (short time)	Thursday, December 20, 2012, 7:00 PM
"F"	Full date/time pattern (long time)	Thursday, December 20, 2012, 7:00:00 PM
"g"	General date/time pattern (short time)	12/20/2012, 7:00 PM
"G"	General date/time pattern (long time)	12/20/2012, 7:00:00 PM
"M", "m"	Month/day pattern	December 20
"O", "o"	ISO 8601 pattern	2012-12-20T18:00:00.000Z
"R", "r"	RFC 1123 pattern	Thu, 20 Dec 2012 18:00:00 GMT
"t"	Short time pattern	7:00 PM
"T"	Long time pattern	7:00:00 PM
"Y", "y"	Year month pattern	December 2012

Percentage formatting

console.log(i18n`Hello ${name}, the percentage is ${0.01}:p.`)
// Hello Steffen, the percentage is 1%.

console.log(i18n`Hello ${name}, the percentage is ${0.005}:p(1).`)
// Hello Steffen, the percentage is 0.5%.

i18nConfig({
    locales: 'de-DE'
})
console.log(i18n`Hello ${name}, the percentage is ${0.01}:p.`)
// Hello Steffen, the percentage is 1 %.

Number formatting

console.log(i18n`Hello ${name}, the number is ${12345.678}:n(2).`)
// Hello Steffen, the number is 12,345.67.

i18nConfig({
    locales: 'de-DE'
})
console.log(i18n`Hello ${name}, the number is ${12345.678}:n(2).`)
// Hello Steffen, the number is 12.345,67.

Pluralization

You can use nested templates for pluralization as shown in this example.

Nested templates

let hello = [
    { name: "Steffen", percentage: 0.2 },
    { name: "Jack", percentage: 0.8 }
]

console.log(i18n`
    <users>
    ${hello.map((item) => i18n`
        <user name="${item.name}">${item.percentage}:p</user>
    `).join('')}
    </users>
`)
// <users>
// 
//     <user name="Steffen">20%</user>
// 
//     <user name="Jack">80%</user>
// 
// </users>

NOTE: For easy translation of multiline template literals use one of the following json schema generators.

Standard format strings

You can add custom standard formatters similar to the predefined DateTime formatters. Valid types are date, number and string.

i18nConfig({
    standardFormatters: {
        number: {
            x: (locales, numberOptions, value) => value.toLocaleString(locales, Object.assign({}, numberOptions, { style: 'percent' }))
        }
    }
})

console.log(i18n`${0.77}:n(x)`)
// 77%

Translation Groups

Translation groups can be very useful to group translations by context. It can also be useful to avoid key duplicates in larger projects. You can use babel-plugin-i18n-tag-translate to inject the relative path of your module as group name. Babel will inject const __translationGroup = 'relative/path/to/module.ext' into each module.

Babel generated file module groups

Example

.babelrc

{
  "plugins": [
    ["i18n-tag-translate", {
      "groupDir": "./src"
    }]
  ]
}

Project Structure

.
├── src
|   └── components
|       ├── App.js
|       └── Clock.js
├── .babelrc

translations.de.json

{
    "components/App.js": {
        "Welcome": "Willkommen"
    },
    "components/Clock.js": {
        "Time": "Zeit"
    }
}

App.js

i18n(__translationGroup)`Welcome` // Select translation from module group e.g. "components/App.js"
i18n('components/Clock.js')`Time` // Select translation from a custom group

i18nGroup Class Decorator

import { i18nGroup } from 'es2015-i18n-tag'

/* default syntax */
class Clock {
    tick() {
        return this.i18n`Time: ${new Date()}:t(T)` // you have to use the class instance of i18n to get the grouped translation
    }
}
export default i18nGroup(__translationGroup)(Clock)


/* experimental class decorator syntax */
@i18nGroup(__translationGroup)
class Clock {
    tick() {
        return this.i18n`Time: ${new Date()}:t(T)` // you have to use the class instance of i18n to get the grouped translation
    }
}
export default Clock

Configuration Groups

Configuration groups should be used by libraries to avoid configuration overrides. Configuration groups are like namespaces and only applied if the group name is set via i18n tag or i18nGroup decorator.

i18n Option

i18n(__translationGroup, 'my-lib')`Welcome` // Select translation from module group e.g. "components/App.js"
i18n('components/Clock.js', 'my-lib')`Time` // Select translation from a custom group

i18nGroup Class Decorator

import { i18nGroup, i18nConfig } from 'es2015-i18n-tag'

i18nConfig({
    locales: 'de-DE',
    group: 'my-lib' // set translation and i18n config for 'my-lib'
    translations: {
        "components/App.js": {
            "Welcome": "Willkommen"
        },
        "components/Clock.js": {
            "Time": "Zeit"
        }
    }
})

/* default syntax */
class Clock {
    tick() {
        return this.i18n`Time: ${new Date()}:t(T)`
    }
}
export default i18nGroup(__translationGroup, 'my-lib')(Clock)


/* experimental class decorator syntax */
@i18nGroup(__translationGroup, 'my-lib')
class Clock {
    tick() {
        return this.i18n`Time: ${new Date()}:t(T)`
    }
}
export default Clock

Translating without template literals

If you have to translate variables that cannot be put into a template literal, you can use the i18n.translate() helper function.

Simple string translation

i18n.translate('Welcome')

var somVar = 'translationkey'
i18n.translate(somVar)

Using formatters

const name = 'Steffen'
const amount = 1250.33

i18n.translate('Hello ${0}, you have ${1} in your bank account.', name, { value: amount, formatter: 'c'})

i18n.translate('Total: ${0}', { value: amount, formatter: 'd', format: 2})

Using config and translation groups

i18n(__translationGroup, 'my-lib').translate('Welcome') // Select translation from module group e.g. "components/App.js"
i18n('components/Clock.js', 'my-lib').translate('Time') // Select translation from a custom group

class Clock {
    tick() {
        return this.i18n.translate('Time: ${0}', { value: new Date(), formatter: 't', format: 'T' })
    }
}
export default i18nGroup(__translationGroup, 'my-lib')(Clock)

Translations as CommonJS Modules

If you are working on a multilingual library it might be useful to export i18n settings and translations as CommonJS modules. This can be easily accomplished with webpack and json-loader as shown in this example:

Example

./my-lib/de/index.js

import translations from 'json!../../translations/translation.de.json'

i18nConfig({
    locales: 'de-DE',
    group: 'my-lib' // set translation and i18n config for 'my-lib'
    number: { 
        currency: 'EUR'
    },
    translations
}) // set internationalization settings and add imported translations

./my-lib/index.js

@i18nGroup('', 'my-lib')
class Clock {
    tick() {
        return this.i18n`Time: ${new Date()}:t(T)`
    }
}

Import library with german translations into an app

import my-lib from 'my-lib'
import 'my-lib/de' // import german i18n configuration and translation

Tools

Build time translation

babel-plugin-i18n-tag-translate: Translate your template literals at build time or add filename groups

JSON Schema

i18n-tag-schema: JSON Schema based translation validation and tools
vscode-18n-tag-schema: Visual Studio Code Extension for JSON Schema based translation validation and tools