Ask HN: What is your favorite Javascript UI framework out there ?

>A UI framework is only as good as the widgets it ships with

Completely wrong. A UI framework is only as good as the widgets it lets you build, and how much it helps you while building them. I have never yet worked on a project where I could piece together all the widgets from one library that perfectly fit every use case.

jQuery UI made a few smart decisions in how to build their API. They kept it extremely jQuery-like, so if you are familiar with jQuery coding style you will be right at home. Everything is tied into the jQuery enhanced set object, built for chaining whenever possible, and relies on no external objects.

Instead of opting to build 40 widgets, 90% of which you won't need for your project and the other 10% which will only fit some of your needs, the pattern you will see is behavior enhancement. This is what gives you the power to build something more powerful than a cookie cutter widget, with only a few short declarations. You can make something draggable, then sortable, then droppable. You can make something else resizable, draggable, and selectable. You can tie all of these things together with the powerful event and method system, and make something that is greater than the sum of its parts. Then you get the bonus of everything being easily themeable with Themeroller.

I feel like web designers are too often stuck in the mindset of imitating desktop UI's, saying "I need this exact kind of treeview" or "This should be a grid, and this a combobox, and these have to be tabs" when they could be considering all the ways that JavaScript, jQuery, and CSS let you step completely out of this box and make something fresh. Things that have become mini-trends in website UIs like the expandy horizontal accordions or Apple's product scroller are what happens when you apply familiar behaviors to new things. In my experience, jQuery UI has allowed me to be the most creative out of any UI framework, and is the best suited for getting interesting stuff done.

The licensing is quite clear. If you'd like to benefit from their work for free you must ensure that you pass on your work for free to your users too.

If you want to make money out of their work you must pay them.

Now whether you like such terms are not is a different story entirely.

jQuery UI:

If you're building a "web 2.0" type web application, jQuery UI is a good fit in my experience. It is lightweight for a UI library and if you're already familiar with jQuery you'll feel right at home. I'm working on such an application right now.

I have to say that the documentation explaining how to create your own widgets is sorely lacking. I hope to write something soon on this subject.

Ext JS:

If you're building a monster web app for intranet / corporate use with a 'desktop application' type of GUI rather than a web friendly interface, Ext JS is an extremely powerful solution. It has ridiculously powerful widgets (the Grid for example). Everything is event driven and class based. Making new widgets or extending core ones is easy through inheritance.

I've worked on 3 such applications so far and it's been great. The documentation is top notch and it's actively supported.

It is however VERY heavy. Both in terms of size and in terms of the markup it generates. Like I said, not for lightweight apps. Build your application completely in JavaScript and forget about html with this one.

If you use Java it is a no-brainer: GWT. You can check out our app for an example: http://demo.teampostgresql.com. It is a fairly complex AJAX app written 99% in plain Java. GWT automatically compiles the source to JavaScript targeting different browsers. Awesome.

MooTools