Originally built as an add-on library extension of YUI by Jack Slocum, Ext includes interoperability with jQuery and Prototype. As of version 1.1, Ext retains no dependencies on external libraries, instead making their use optional.
While working on extjs did some research related to ext js lib and other js libraries like jquery,dojo…. and found that extjs is heavier than jquery and other js framework/toolsets on the webpage ….
There a guy named saki………(http://blog.extjs.eu/)
He has made some excellent plugins using extjs … have a look….http://examples.extjs.eu/