So the homegrown editor that I am working on has three main component: A file browser and the actual editor and an editor server.
Server is responsible for serving files and provide information about the file system. File browser gets the list of files and directories from the server and displays those. Editor opens files and allows editing and saving them.
jQuery is like a must for any front-end work. For my file browser, I wanted to use jQueryUI for display a list of files with autocomplete feature. However, soon enough I realized that jQuery autocomplete feature is way too slow when it comes to large lists. For example when I tried to list things in /usr/bin, things got very ugly and slow, very fast! I really hated the slowness and decided to develop my own autocomplete UI and it turns out very very nice.
For making the UI nice and pretty I am using bootstrap. I am very impressed by this library. Very well done. I have to say bootstrap IMHO is superior to jQueryUI themes.