JS: Iterator.prototype.forEach

(new in JS: ECMAScript 2025)

iterator.forEach(f)

• Apply function f to every yield in Iterator iterator.
• Return undefined.

Normally you can use this method on any Iterable, because all standard iterable objects are also Iterator.

• f is given args:
• currentElement
• currentIndex

similar to JS: Array.prototype.forEach

// define a generator function
function* gf() {
  for (let x of Array(5).fill(0)) yield x;
}

// create a generator (is an iterable)
const gg = gf();

// use method forEach
const hh = gg.forEach((x, i) => console.log(x, i));
/*
0 0
0 1
0 2
0 3
0 4
*/

console.log(hh === undefined);
// true