[playworker]

Yes, you probably want something like CodeMirror https://codemirror.net/

[joshmarlow]

I'd second CodeMirror - I've been tinkering with it (v2 - https://codemirror.net/2/) for a couple of weeks and it's pretty nice to use. I'm using a bit of simple syntax highlighting.

There's also a react wrapper (for versions 1 and 2).