(If you're asking about what flavor of Javascript I use) I just use plain JS for the bits of JS I need, but nothing I have been working on needs a heavy front-end.

There's not really an Elixir equivalent of Clojurescript to Clojure (there is an Elixirscript, but it's a work in progress and I'm curious whether it can ever capture the nice experience of using the Erlang VM). I've seen interest in the Elixir community in Elm and Bucklescript(OCaml) and other compiled-to-js languages, but I think a lot of people just use JS.

I know you weren't asking me, but Elm on the front end, communicating to Elixir on the back end, has made my life so much nicer. I loathe JavaScript, and this Elm/Elixir combination has made me like web programming again.