Closure Library

The Closure Library is a broad, well-tested, modular, and cross-browser JavaScript library. You can pull just what you need from a large set of reusable UI widgets and controls, and from lower-level utilities for DOM manipulation, server communication, animation, data structures, unit testing, rich-text editing, and more. The Closure Library is server-agnostic and is intended for use with the Closure Compiler. The Closure Library serves as the base JavaScript library for many Google products. Now that the Closure Library is open source, more and more developers outside Google are integrating the library in their own projects. If you are developing a large or growing application, you may benefit from the Closure Library's breadth. A well-tested library can insulate you from cross-browser compatibility issues and the minutiae of client-side programming, letting you focus on the fun stuff.