Ask HN: Creating an online IDE, looking for a JS framework

I'm creating a small online IDE, like Cloud9's, as a hobby project. I'm using Go for the server side and my API is ready. Now, the hard part: Javascript!

I've been looking for a versatile window/panel based framework, but i could only find the heavyweight stuff: ExtJS, Dojo, etc. Do you guys know a lightweight framework that features resizable/dockable panels, but allows me to work with simple HTML & CSS, instead of dealing with unnecessary stuff (like Ext, for example)?

ps.: I'm using the Ace Editor, btw. Amazing project.