That's a poisonous chalice not the holy grail. How can someone to prefer JS to Swift is beyond my comprehension. Or is that "if the only tool you have is a hammer" situation?

I haven't tried Reactive Native or other options, but my gut tells me it's less safe to write in Javascript than Swift. What would be an advantage that outweighs that?

Less safe in what sense?

Type safety & all that jazz. Swift is a much more powerful language than javascript (and typescript) is.

Why? JS is crap compared to Swift. There are various technologies that allow you to do that anyway(i.e nativeScript)

Getting closer with React Native.

Some are already dong this with Apple's JSCore.

There's already NativeScript and React Native.