I have found it\'s very hard to find documentation about Gnome Shell Extensions. I found some bits on Gnome Wiki (and it\'s first-level links), but it\'s not much:
http:
Well, supposedly, with Gnome3, you have a pretty uniform API across various programming languages, that is generated from the same GIR files. So you should (at least in theory) be able to retrieve all the API - I hope with documentation - from the GObject Introspection. And the other way round, you should be able to transform example code from another language into JavaScript for this API easily.
Theoretically. I avoid JavaScript where possible, developing a desktop application in JavaScript is the last I would do.