Yahoo! User Interface Library

Web site: http://developer.yahoo.com/yui/

License: BSD

The Yahoo! User Interface Library is a large JavaScript API that provides support for all aspects of rich-application development. It includes event management, drag-and-drop support, visual effects, animation, and AJAX communications. It also includes a number of widgets (which are called controls); these include an AutoComplete search widget and a calendar widget. The AJAX API is document-based on a single asyncRequest method. AJAX form submission is supported, and an object-oriented API for managing connections and errors is provided. The library includes excellent documentation; it also includes a design patterns library that shows how to combine the various widgets and effects.