Any language that compiles to JavaScript.
https://flak.tedunangst.com/post/technical-debt-and-tacking-...
> lessons learned:
> Those who don’t learn from history are doomed to repeat it. Any day now, I suspect some fools are going to want to write web apps, but they won’t want to use raw javascript and they’ll create some ridiculous custom language to javascript compiler. I can only hope they have the good sense not to tell anybody about it.