If you don't limit yourself to a strictly JS UI library, you can try NOLOH (http://www.noloh.com http://www.noloh.com). NOLOH stands for Not One Line of HTML an

If you don't limit yourself to a strictly JS UI library, you can try NOLOH (http://www.noloh.com http://www.noloh.com). NOLOH stands for Not One Line of HTML and allows you to work on a single language on the server-side without ever having to deal with the client. Unlike SproutCore, or Cappuccino, which are fat-clients, NOLOH is lightweight and on-demand. This means that your application loads instantly (noloh.com is a noloh app), and there's never any unnecessary code loaded on the client at any time, either on the server, or client. Best of all this is done automatically for you completely transparent to the developer. Furthermore, all the native widgets & core for that matter are completely skinnable, extendable, and modifiable as you can see from the vast visual differences and feel in the numerous NOLOH applications. NOLOH also allows you to easily use most 3rd party JavaScript widgets & components out of the box, without a single line of modification to the 3rd party library. You can see how easy that is at http://github.com/noloh http://github.com/noloh, take SyntaxHighlighter for example. If you have large set of legacy HTML, no worries, NOLOH allows you to work with that and seamlessly communicate with the server check out a demonstration here: http://www.youtube.com/phpframework#p/c/C102458C2FFD8ACF/5/ifcWydvrMOk http://www.youtube.com/phpframework#p/c/C102458C2FFD8ACF/5/i... Also, unlike Sproutcore or Cappuccino, the client is only used for rendering and not a store of your business logic. So all your valuable application logic is completely protected from prying eyes. For all that are wary about NOLOH, give it a watch at http://youtube.com/phpframework http://youtube.com/phpframework to see simple and efficient it really is. We've been around since 2005 (though only available to the public since last year) and have a growing set of articles & videos. In the coming month we'll have more demos than you'll know what to do with. Disclaimer: I'm a co-founder of NOLOH. [edited for clarity]