Aja.js
Ajax without XML : Asynchronous JavaScript and JavaScript/JSON(P)
Forerunner Db
A JavaScript database with mongo-like query language, data-binding support, runs in the browser as a client-side DB or on the server via Node.js!
Dygraphs
Interactive visualizations of time series using JavaScript and the HTML canvas tag. The dygraphs JavaScript library produces interactive, zoomable charts of time series.
Jszip
Create, read and edit .zip files with Javascript
Sheetrock
Quickly connect to, query, and lazy-load data from Google Spreadsheets.
Smoothie
Smoothie Charts: smooooooth JavaScript charts for realtime streaming data
Dc.js
Multi-Dimensional charting built to work natively with crossfilter rendered with d3.js
Datamaps
Maps for interactive data visualizations in Javascript
Countable
Countable is a JavaScript function to add live paragraph-, word- and character-counting to an HTML element.
Lowdb
An extendable JSON database for Node and the browser powered by lodash
C3
A D3-based reusable chart library
Tiny Slider
Vanilla javascript slider for all purposes.
Tabletop
Tabletop.js gives spreadsheets legs
Convnetjs
Deep Learning in Javascript. Train Convolutional Neural Networks (or ordinary ones) in your browser.
Clusterize.js
Tiny vanilla JS plugin to display large data sets easily
jQuery File Upload
File Upload widget with multiple file selection, drag&drop support, progress bars and preview images for jQuery. Supports cross-domain, chunked and resumable file uploads and client-side image resizing. Works with any server-side platform (PHP, Python, Ruby on Rails, Java, Node.js, Go etc.) that supports standard HTML form file uploads.
Local Forage
Offline storage, improved. Wraps IndexedDB, WebSQL, or localStorage using a simple but powerful API.