global
ignore case

Well, one call to match is performed in O(N) and you cannot solve the problem faster.
But it also allocates extra O(N) memory only to take the length of the array[-ish structure] later.

TIME = O(N), optimal

MEM = O(N), non-optimal, O(1) is possible.

That's 2 to the power of 19

One doesn't need to use built-in toString method because the problem cannot be solved with direct computation anyway. Some (school level) math knowedge is required.

Use radix or _base

its cool to come 3 years later and complain about version.

10 years ago I was also saving each extra loop iteration, making code better as I thought. That's called premature optimiztion and highload is about scalability rather than constant time factor.

"VOL." is still a problem in JavaScript.

It uses Uint8Array which is low-level machine array.

That's what was used in Doom (yes, original Doom 1). Instead of calculating sin/cos they had a table.

Overall code isn't production-grade, but nice use of tail recursion.

Actually the thing is it cannot be solved w/o some math.
Knowing math, there's not much of a programming here, thoug—I agree on that.