Intern is a complete test system for JavaScript designed to help you write and run consistent, high-quality test cases for your JavaScript libraries and applications. It can be used to test any JavaScript code. It can even be used to test non-JavaScript Web and mobile apps, and to run tests written for other test systems.

A JavaScript framework for building data-driven React applications.
Never again communicate with your data store using an imperative API. Simply declare your data requirements using GraphQL and let Relay figure out how and when to fetch your data.
Queries live next to the views that rely on them, so you can easily reason about your app. Relay aggregates queries into efficient network requests to fetch only what you need.
Relay lets you mutate data on the client and server using GraphQL mutations, and offers automatic data consistency, optimistic updates, and error handling.

Ember.js is an open-source JavaScript web framework, based on the Model–view–viewmodel (MVVM) pattern. It allows developers to create scalable single-page web applications by incorporating common idioms and best practices into the framework.

React Native lets you build mobile apps using only JavaScript. It uses the same design as React, letting you compose a rich mobile UI from declarative components.

Enzyme is a JavaScript Testing utility for React that makes it easier to assert, manipulate, and traverse your React Components' output.

A minimalistic framework for server-rendered React applications

A library to generate PDFs in client-side JavaScript.

meSing.js is a JavaScript singing synthesis library that uses the Web Audio API's DSP capabilities in conjunction with the meSpeak.js speech synthesis library to provide a vocal synthesizer for the web.

Service Worker Precache is a module for generating a service worker that precaches resources. The module can be used in JavaScript-based build scripts, like those written with gulp, and it also provides a command-line interface. You can use the module directly, or if you'd prefer, use of the wrappers around sw-precache for specific build environments, like webpack.

It can be used alongside the sw-toolbox library, which works well when following the App Shell + dynamic content model.

A collection of service worker tools for offlining runtime requests

Tesseract.js is a pure Javascript port of the popular Tesseract OCR engine.

This library supports over 60 languages, automatic text orientation and script detection, a simple interface for reading paragraph, word, and character bounding boxes. Tesseract.js can run either in a browser and on a server with NodeJS.

Fast, reliable, and secure dependency management tool for javascript.

Hyperform is a complete implementation of the HTML 5 form validation API in Javascript. It replaces or polyfills the browser’s native methods and eases your validation task with custom events and hooks.

Feathers is a real-time, micro-service web framework for NodeJS that gives you control over your data via RESTful resources, sockets and flexible plug-ins.

Passport is authentication middleware for Node.js. Extremely flexible and modular, Passport can be unobtrusively dropped in to any Express-based web application. A comprehensive set of strategies support authentication using a username and password, Facebook, Twitter, and more.

WebTorrent is a streaming torrent client for the web browser and the desktop.

WebTorrent is written completely in JavaScript – the language of the web – and uses WebRTC for peer-to-peer transport whenever possible. No browser plugins, extensions, or installation is required to use WebTorrent in your browser.

A terminal built on web technologies : JS / HTML / CSS

A fast, in-memory document-oriented datastore for node.js, browser and cordova

This is a game designed to teach JavaScript and artificial intelligence in a fun, interactive way.

You play as a warrior climbing a tall tower to <insert something that motivates you here> at the top level. On each floor, you need to write JavaScript (with full ES2015 support) to instruct the warrior to battle enemies, rescue captives, and reach the stairs.

Experimenting with window.onerror, trying to make JavaScript debugging easy.
What does it do?

Provides JavaScript error details in a readable format. You can log these errors remotely by enabling remoteLogging. After enabling, logerr will send a post request to the desired action/url with exception details along with custom parameters (if provided using additionalParams).