[Wowfunhappy]

It's the only kind of JIT'd code you're allowed to run on iOS without going through Apple's approval process. Pebble apps use JS for any code they need to run on the phone (as opposed to the watch) for this reason.

[saagarjha]

(Technically there's also WebAssembly as of recently, but it's part of JavaScriptCore so this is somewhat pedantic.)