jQuery is a fast, small, and feature-rich JavaScript library. It makes things like HTML document traversal and manipulation, event handling, animation, and Ajax much simpler with an easy-to-use API that works across a multitude of browsers. With a combination of versatility and extensibility, jQuery has changed the way that millions of people write JavaScript.

AngularJS HTML enhanced for web apps! AngularJS is a structural framework for dynamic web apps. It lets you use HTML as your template language and lets you extend HTML's syntax to express your application's components clearly and succinctly. Out of the box, it eliminates much of the code you currently write through data binding and dependency injection. And it all happens in JavaScript within the browser, making it an ideal partner with any server technology.

Vue.js is a library for building interactive web interfaces. It provides data-reactive components with a simple and flexible API.

Dojo is an Open Source DHTML toolkit written in JavaScript. It builds on several contributed code bases (nWidgets, Burstlib, f(m)), which is why we refer to it sometimes as a "unified" toolkit. Dojo aims to solve some long-standing historical problems with DHTML which prevented mass adoption of dynamic web application development.

Raphael is a small JavaScript library that should simplify your work with vector graphics on the web. If you want to create your own specific chart or image crop and rotate widget, for example, you can achieve it simply and easily with this library.

DHTMLX Suite JavaScript Component Library for Building Rich Web Apps. dhtmlxSuite is a JavaScript library that provides a complete set of Ajax- powered UI components. Use dhtmlxSuite to build enterprise-level web apps with clean interface, fast performance, and rich user experience.

MooTools is a compact, modular, Object-Oriented JavaScript framework designed for the intermediate to advanced JavaScript developer. It allows you to write powerful, flexible, and cross-browser code with its elegant, well documented, and coherent API. MooTools code respects strict standards and doesn't throw any warnings. It's extensively documented and has meaningful variable names: a joy to browse and a snap to understand.

Modernizr is a small JavaScript library that detects the availability of native implementations for next-generation web technologies, i.e. features that stem from the HTML5 and CSS3 specifications. Many of these features are already implemented in at least one major browser (most of them in two or more), and what Modernizr does is, very simply, tell you whether the current browser has this feature natively implemented or not.

php.JS helps to use PHP functions in JavaScript. php.js is an open source project that brings high-level PHP functions to low-level JavaScript platforms such as web browsers, browser extensions (Mozilla/Firefox, Chrome), AIR, and SSJS engines like V8 (node.js, v8cgi), Rhino, and SpiderMonkey (CouchDB)

Sizzle is a pure-JavaScript CSS selector engine designed to be easily dropped in to a host library.

Prototype is a JavaScript Framework that aims to ease development of dynamic web applications. Featuring a unique, easy-to-use toolkit for class-driven development and the nicest Ajax library around, Prototype is quickly becoming the codebase of choice for web application developers everywhere.

jqPlot is a plotting and charting plugin for the jQuery Javascript framework. jqPlot produces beautiful line, bar and pie charts with many features. jqPlot's Strongest Feature is its Pluggability! Computation and drawing of lines, axes, shadows even the grid itself is handled by pluggable "renderers". Not only are the plot elements customizable, plugins can expand functionality of the plot too! There are plenty of hooks into the core jqPlot code allowing for custom event handlers, creation of new plot types, adding canvases to the plot, and more!

jsMorph is a morphing - motion - tweening framework that knows what you need to do... get going! It's a nice ensemble of best timing, fast, smart and resource saving algorithms and convenience. jsMorph is a completely Cross-Browser, pure javaScript animation framework that can manipulate almost any and multiple stylings of multiple HTML elements. It auto detects start positions, auto converts units, automatically adjusts rendering speed and corrects time leaks for smoother rendering experience.

PHPlot is a graph library for dynamic scientific, business, and stock-market charts. PHPlot allows PHP developers to create pie charts, bar graphs, line graphs, point graphs, etc. from a PHP application. PHPlot is a specialized graphics library which provides a means for your PHP-enabled web server to create and manipulate graphs as objects and display the completed graph as an image. PHPlot uses the GD library to create elementary shapes such as lines, rectangles, and text, but hides the details of GD from the application programmer.

PaintbrushJS is a lightweight browser-based image processing library built with Javascript and canvas.

YUI Library is a set of utilities and controls, written with JavaScript and CSS, for building richly interactive web applications using techniques such as DOM scripting, DHTML and AJAX. YUI is proven, scalable, fast, and robust. Built by frontend engineers at Yahoo! and contributors from around the world, it's an industrial-strength JavaScript library for professionals who love JavaScript.

DropzoneJS is an open source library that provides drag'n'drop file uploads with image previews. It's lightweight, doesn't depend on any other library (like jQuery) and is highly customizable.

LESS is a dynamic stylesheet language. LESS extends CSS with dynamic behavior such as variables, mixins, operations and functions. LESS runs on both the client-side (Chrome, Safari, Firefox) and server-side, with Node.js and Rhino.

Elycharts is a pure javascript charting library, easy to use and completely customizable. It helps you create good looking interactive charts on you web pages or web applications, with a lot of useful features: legend and label support, mouse tracking, tooltips, templates, animations

JSZip helps you create .zip files with Javascript. JavaScript today is capable of generating a lot of data. The easiest way to deliver multiple files to your users is in a zip file. Instead of wasting server resources and bandwidth you can get the client to do it for you by JSZip.