forEach (for Iterators)

Creates a function that consumes an iterator and runs a callback for each element. Use it with pipe.

pipe(source, forEach(callback));

::: info

In ordinary code, prefer the native Iterator.prototype.forEach: source.forEach(callback). Use this es-toolkit/fp/iterator variant when composing transformations with pipe.

:::

Usage

forEach(callback)

forEach is a terminal step for side effects: it pulls every element and runs callback on each. Because it consumes the whole iterator, it must not be used on an infinite iterator. It delegates to the native Iterator.prototype.forEach.

import { pipe } from 'es-toolkit/fp';
import { filter, forEach } from 'es-toolkit/fp/iterator';

// Log each even number.
pipe(
  [1, 2, 3, 4].values(),
  filter(x => x % 2 === 0),
  forEach(x => console.log(x))
);
// Logs: 2, 4

Parameters

• callback ((value: T, index: number) => void): Called with each element and its index.

Returns

((source: Iterator<T>) => void): A function that consumes an iterator and returns nothing.