If you want complete type erasure, then a system that ensures monomorphism is critical to good JS performance. If you can leave the type system in place, then

If you want complete type erasure, then a system that ensures monomorphism is critical to good JS performance. If you can leave the type system in place, then you could move toward an ML-style type system and see massive improvements within strictly-typed parts of the code as you'd only need type guards and inline caches at the boundaries of the strictly-typed code.