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://live.gnome.org/GnomeShell/Extensions
The problem here is GJS and it's bindings. Absolutely no documentation, got lot's of SIGSEGVs, binding is just not ready (GLib, Gio and others). The only working one is unofficial documentation generated from GIR for Seed JavaScript implementation:
http://roojs.org/seed/gir-1.2-gtk-2.0/seed/
Where to get more examples? I want read directories, files, spawn processes, open network sockets and do other stuff.
Update: Show me how to read a file line by line in GJS. According Google this is not possible. Thanks.