You can though. Chrome dev tools can edit local files. It's basically an IDE. You can easily build a single page application. You can even do some server-like stuff purely in the browser now with service workers. There are also plenty of online IDEs available spanning the gamut from toys to serious work environments.
For anyone that doesn't know that, open dev tools > Sources > Filesystem > + (Add folder to workspace) > right-click on folder > New file. Then double-click on file to open it for editing and save modifications with Ctrl-S. Of course it isn't an IDE, with even the editor being nothing more than a Notepad clone, and you're limited to client-side work which is in contrast to what OP seems to want.
