Dojo is a modular JavaScript toolkit with an extremely 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, it provides one of the largest collections of optional modules supporting things such as a widgeting 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 simplfy deployment and improve performance.