Hi,
Have you seen this thread: Playdate SDK with TypeScript ?
Perhaps your JS code is compatible with TS? (I know little about the two).
Lua and C are the only two officially supported languages, it looks like, so Lua probably is the way to go if you don't want to go too low level. I also tried using C++ but it's not officially supported and requires extra steps, I think every non official language will do.
Cheers