Why would you be using JS in this scenario?

I was under the impression that modern compilers just inline something like that, and even in older languages (like C) use trickeries are used to inline it (typically MAX is a macro rather than a real function, so its always inlined)

Ultimatelly it depends not just on what you're doing but also the language and compiler you're using.

If you're optimizing that hard you should probably sort the data first anyway, but yeah, sometimes it's absolutely called for. Not that I've actually needed that in my professional career, but then again I've never worked close enough to metal for it to actually matter.

That said, all of these are implemented as functions, so they're already costing the function call anyway...

Sometimes, but practically never. Just be a thief.