The Dojo Toolkit is a modular JavaScript toolkit that makes building richer web UI's much easier.

Dojo builds on a fast, lightweight base that provides a competitive set of features (DOM traversal, AJAX, animations, event handling) at the same size as many of the alternative "lightweight" toolkits.

On top of that base Dojo provides easy access to an extensive collection of optional modules, including a widget framework that focuses on accessibility and internationalization, 2D and 3D charting and vector graphics, advanced math functions, offline capabilities, cryptography, and much much more. It also comes with a build system that collects and minifies your files into layers that you can include in your page as needed to simplify deployment and improve performance.