It'd be nice is someone made a general text editor that was also embeddedable and could also live edit itself (or the program it's running in). The closest I've seen is Nightlight https://sekao.net/nightlight/
But it's not really "general purpose" like Emacs w/ Elisp and it's pretty Clojure specific
https://beta.observablehq.com/ https://glslsandbox.com https://shadertoy.com https://codesandbox.io/ https://codepen.io/ https://codeanywhere.com/ https://codeshare.io/ https://www.codechef.com/ide https://js.do/ https://codebunk.com/ https://stackblitz.com/ https://coder.com/ https://www.remoteinterview.io/codepad https://vertexshaderart.com https://greggman.com/downloads/examples/html5bytebeat/html5b... https://glitch.com/ https://jsbin.com/ https://jsfiddle.net/ https://webglfundamentals.org
We recently created a web interface for docker swarm as part of a university project, part of our requirements were that a compose file could be submitted via the web interface to create a new stack. We used ace for this and it worked quite nicely.
* parser - https://prettydiff.com/parse-framework/runtimes/browsertest....
By turning off Ace and turning it back on you can experience a huge change in user experience
https://github.com/dropbox/hackpad/tree/master/etherpad/src/...
https://github.com/ether/pad/tree/master/infrastructure/ace
> ACE2 is EtherPad's editor, a content-editable-based rich text editor that supports IE6+, FF(2?/)3+, Safari(3?/)4+. It supports collaborative editing using operation transforms (easysync2), undo/redo, copy/paste.
> The name "ACE2" is because this is a rewrite of aiba's original content-editable AppJet Code Editor.