JS: Iterator.prototype.reduce

(new in JS: ECMAScript 2025)

iterator.reduce(args)

Similar to Array.prototype.reduce , but works on iterator.

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

// define a generator function
function* gf() {
  for (let x of [1, 2, 3, 4, 5]) yield x;
}

const f = (x, y) => `f(${x} ${y})`;

console.log(
  gf().reduce(f) === "f(f(f(f(1 2) 3) 4) 5)",
);
// true