Check out https://reasonml.org - created by Jordan Walke, the creator of React. Reason offers the best of both worlds - type safety without getting in the way and faster JS than what you'd write by hand.
You can leverage ocaml/ml as well as js ecosystem. Mix different files and syntax.
Bsb is also faster than tsc.
- non-standard ordering of arguments between belt/standard library
- Ocaml's standard library actually generally avoiding the Option/Result type, in preference of exceptions, which is unexpected and a pain since it's an ML.
- package management involves manually adding things to the bsconfig (has this changed?)
- things randomly break between relatively minor Bucklescript versions, they broke something pretty important in like a .x release when I was messing around with it
- server side isn't good. It technically works but all the bindings are old or terribly documented, and you never really know if it's not going to blow up at some point.
Otherwise, I actually quite like it! None of those are actual core language complaints.