[gsnedders]

JS has less dynamism in various places (operators especially, which allows you to statically type more, and therefore elide guards).

But yeah, I very much agree: Python isn't special here, it's just a willingness to spend resources (though a lot of that is tied to the CPython C API: either you constrain your VM design choices to be compatible with it directly, or have to add overheads to any/many C API calls).