Even more powerful, though, is autocomplete from the running environment. It means that (just like in the Chrome Dev Tools) when you start typing something, the autocomplete suggestions include all of the valid names that are defined. It really helps in navigating complex APIs like Torch: https://www.dropbox.com/s/e6hriw5quwct65a/Screenshot%202015-...
Thinks like tern.js[0] or my own Aulx[1] provide that with varying success. Visual Studio's JS autocompletion is also stellar. The techniques used could be applied (with tweaks) to most dynamic languages.
https://www.youtube.com/watch?v=II1PgYTPW_U
I need to do another video soon, the work has progressed a bit further since then.