[josephg]

Just because we’re on the topic of performance: the rust optimizer can sometimes generate better code if you use map / filter / etc. The slice iterator in any context is a huge win over manual array iteration because it only needs to do bounds checking once.

Javascript (v8, last I checked) is the opposite. Simple for loops almost always outperform anything else.

[duckerude]

I've seen cases where an iterator was better, but I've also seen gains from using an imperative loop with manual indexing. Loop conditions and the occasional assertion can be enough to elide bounds checks. (Though sometimes the compiler gets too paranoid about integer overflow.)

Most of the time you should just write whatever's clear/convenient but sometimes it's worth trying both and scrutinizing godbolt.

[baby]

This is premature optimization imo. Unless you’re using par_iter

[josephg]

Without knowing the domain, you have no way of knowing that.

It’s also much easier to stick to for() loops in javascript as you code than it is to rewrite everything later when tuning for performance. If that’s something you expect to need to do.