Javascript Library - Dojo - The javascript toolkit

The Dojo Toolkit is an open-source JavaScript toolkit for building great web applications. It shortens the time between idea and implementation by providing a well conceived API and set of tools for assisting and fixing the issues experienced in everyday web development. It is lightning fast, extremely robust, and supplies a solid set of tools for DOM manipulation, Animations, Ajax, Event and keyboard normalization, Internationalization (i18n) and Accessibility (a11y). The Base of Dojo is a single, lightweight entity (26KB "across the wire"). Dojo is completely free, liberally licensed (AFL or BSD), and transparently developed by an active group of developers with a strong community presence.

No matter the size of your projects, Dojo is the ultimate scalable solution to your development woes. The built-in package system ends the headache of tracking dependencies, the build system combines and shrinks optimized "layers" of code for deployment, and D.O.H. makes unit and regression testing a breeze.