Discussion on: Don’t pay the for-loop tax

This expands the array and may cause it to reallocate in memory being slow

That's surely correct, but if you're interested in performance you should definitely use a for loop, as any solution based on callbacks, while more expressive, is one or two orders of magnitude slower, for small and large arrays:

console.time("Array.push");
var array = [];
for (var i = 0; i < 1e7; i++) array[i] = i;
console.timeEnd("Array.push");
// Array.push: 220ms

console.time("new Array.push");
var array = new Array(1e7);
for (var i = 0; i < 1e7; i++) array[i] = i;
console.timeEnd("new Array.push");
// new Array.push: 47ms

console.time("Array.map");
var array = [ ...Array(1e7).keys() ].map((_, i) => i);
console.timeEnd("Array.map");
// Array.map: 1209ms

But let's not forget that we also have for...in and, above all, for...of in JavaScript, which bring much nicer semantics.

These are my main cases of why I use for loops in JavaScript:

1. I'm releasing an open source package which could be used in performance-intensive tasks;
2. my code needs to be transpiled and things like for...of are polyfilled with an unbearable amount of code (in the case Babel can't infer if the collection is actually an array or any other kind of iterable);
3. because - ah, screw it - it's clear enough since it's a pattern everyone knows, while building an array with [ ...Array(n).keys() ].map(...) is quite obscure at the first glance.

The rest of the article is pretty much spot-on. Concepts that need to be reiterated.