This itself reminds me of similar performance issues hidden in C++. The float->int cast on x86 with Microsoft's compiler called a helper library function 'ftol'. Turns out this does loads of stuff to be spec compliant. Replacing it with a single not-spec-but-works-for-us x86 assembly instruction to convert was way faster.

So not just JS - it seems language built-ins are often slowed down by bureaucratic spec compliance, and hand-rolling code can help you get a speedup.