This tool provides a lots of facility like models with key-value binding and custom events, API of enumerable functions, views nad other lot of useful rich APIs that helps to create a modern application.
This library in very good for developing complex and cross browser web pages in just simple way.
Sencha Ext JS is the industry's most powerful desktop application development platform with unparalleled cross-browser compatibility, advanced MVC architecture, plugin-free charting, and modern UI widgets.
Serenade.js is a client side framework and create rich client side applications too.
Feathers is one of the most popular light weight web application framework for nodejs. Also create RESTful web services and real-time applications.