> I'm hoping that we can find a GHCJS-based FRP solution at some point soon.

Have you tried Reflex (also there is a try-reflex[1])?

Purescript generates really concise javascript code, have you checked out Thermite[2]?

0: https://github.com/ryantrinkle/reflex 1: https://github.com/ryantrinkle/try-reflex 2: https://github.com/paf31/purescript-thermite