I haven't used Elixir/Erlang personally. I really like the idea of TypeScript, but I ran into a fun bug in one program where I had an object that was declared to be of type "Result" and had gone through at least three calls that said it should be that type, but when I printed the type at the point where it crashed it was actually a string. That caused me to lose some of my faith in TypeScript type checking. It was a JSON string that should have been parsed to a Result, but the parse never happened and the compiler didn't catch it.

I prefer Scala.js. I've written significantly more Scala.js than TypeScript and I've never had anything like that happen in Scala.js.