It would be great to have a web-based live js editor with github integration via the github api, so I could edit files in a repo and do commits without having to leave the editor.
I believe Cloud9 (https://c9.io/) is exactly what you're asking for. Unfortunately I haven't been able to get it to clone any of my repos recently to play around with it a lot but I did try it out awhile ago and it seemed pretty decent.