It's easier to chuck away type information than mystically conjure it out of thin air.
An ahead-of-time compiler can't make JS fast because it lacks the type information needed to do so. That's why you need just-in-time compilation for JS: you can only discover what types go where by running the code.
An ahead-of-time compiler can't make JS fast because it lacks the type information needed to do so. That's why you need just-in-time compilation for JS: you can only discover what types go where by running the code.