rhlsthrm

I'm a full-stack web dev (skewed toward backend), fully focused on Typescript for the past couple of years. I have a pretty solid understanding of OO concepts now, and I've started dabbling in things like Domain-Driven Design, which are (from my understanding), solid extensions of OO. I've fairly recently come across more and more stuff about functional programming and various languages like Scala, Clojure, PureScript, Elixir etc. People seem to have a generally favorable opinion about these. Especially it seems like Elixir/Elm/Erlang (are these all part of the same ecosystem?) have a lot of raving fans.

My question is, what would I get out of learning functional programming? Is there a good tool or language I can learn that will make me immediatly able to apply my learnings to my daily work in backend/frontend web dev?