Technically there is no iteration in filter/map/reduce at all.
Consider this excerpt from the .map() polyfill on MDN:
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Refe...
// 7. Let k be 0
k = 0;
// 8. Repeat, while k < len
while (k < len) {
// [loop body omitted]
// d. Increase k by 1.
k++;
}