EXT JS is an extensive JavaScript library used to produce Rich Internet Applications. It used to use Yahoo User Interface (YUI) and other framework like Prototype and JQuery in the past. But now, it is an independent framework that has a rich set of ready to use components for easy and fast application building.
It has a very good documentation, a strong forum and many other tools such as EXT GWT and EXT Designer. It is a good thing to get started but beware that it has a very high learning curve. Other tools like JQuery and Prototype have a pretty steep learning curve as compared to EXT JS. Whereas, the extensibility in incredible in it and it offers a rock solid platform with less time to spend on building components.
The latest version EXT JS 3.0 has brought new features such as Graph plotting and easy Drag-Drop Portal layouts. These are a real need if you wanna start a professional RIA career in web. It has some applications available in Adobe AIR formats which can be installed in any platform and used for easy development.
Learn more at the site itself.
URL: http://extjs.com
