[rtpg]

Clojurescript has a lot of interesting stuff behind it, but honestly Clojure stuff has a pretty high learning curve (CLI tools whose error messages are extremely unhelpful, docs that are pretty minimal, and other things that make falling off the happy path rough). I think it's a very interesting "serious" choice, especially if you also want to run stuff as Clojure. But I found it a bit hard to get into.

Purescript has, I think, some of the most interesting things going for it from a FP language, as its effects system paired with the very nice support for JS objects through Record means you can build effects systems like "this function reads from the DB" vs "this function writes to the DB", or "this function accesses a single user's data" vs "this function is multitenant". The FFI story is also very straightforward IMO.

ReScript feels close to Elm in that it's very focused on a straightforward usage of ML and isn't trying to be fancy. I haven't messed with it in a while but honestly OCaml is pretty straightforward and lets you easily fallback to simple imperative tricks in a way that Clojurescript and Purescript don't.

I think if you want to go full FP, Purescript has the most interesting stuff to bring to the table (and because it's not lazily evaluated the mental model is not hard). ReScript has the easiest onboarding IMO... and Clojurescript is good if you're into Clojure/lisp-y stuff in general. But they're all very distinct flavors and it's ultimately a bit of an aesthetic choice IMO