Scala.js actually works really well. Frontend people aren't very aware of it, but if you're a backend dev who just needs to write a bit of code that has to run in the browser then I highly recommend it.
Even as an engineer happiest in Scala almost forced to write Typescript, I'll be the first to admit that the Scala.js library is still a bit lacking in comparison for real world productivity.
I had exactly the opposite experience. I kept trying to make Typescript work and it just wouldn't, eventually resorted to Scala.js and found (to my shock) that everything just worked and there were far less random rough edges.
