JavaScript development environment?

For the features you're looking for, the other commenters gave you the two best-bets that I'm aware of. Personally, I use Visual Studio 2010 and really like it, primarily because of the multi-pane, multi-monitor support. In other words, I use it as a really fancy text editor. I do code heavily in ExtJs. For integrated debugging with ExtJs, Firebug is totally indispensible.

Getting started with Ext can be hard. I'd suggest starting with the demos and tweaking the code from there for your needs. The API reference online is very useful. StackOverflow is about on par with the forums for questions.

Good luck.

I use Netbeans, it has really good JavaScript support, all the standard stuff you would expect, plus it reconizes most of the JS libraries and will do auto complete for them. They used to have in IDE Javascript debugging in 6.7 but 6.9 and 7 do not have the plugin, they say it is coming back at some point. It was really nice to set break points in the IDE run the browser and be able to step through the code in the IDE. You could step through the front end, to the back end, to the database, and back again.

Aptana Studio is based on Eclipse: http://www.aptana.com/products/studio3

Another JavaScript IDE is WebStorm: http://www.jetbrains.com/webstorm/

When I use in a proyect js, I use eclipse with a simple java web proyect and tomcat with the javascript files inside the folder etc, but I only use it for some things, so I think you should use what fit to your needs man :D