dropWhile (for Iterators)

Lazily skips the leading elements of an iterator while a predicate holds, then yields the rest.

const rest = dropWhile(source, shouldDrop);

Usage

dropWhile(source, shouldDrop)

Use dropWhile when you want to skip a prefix of elements based on a condition rather than a fixed count — for example, skipping log lines until the first error. Elements are skipped while shouldDrop returns a truthy value; every element from the first failing one onward is yielded, including that element. The native iterator helpers offer drop (by count) but not a predicate-based dropWhile, which is why this is provided.

import { dropWhile } from 'es-toolkit/iterator';

// Skip the leading run of small numbers.
dropWhile([1, 2, 3, 1].values(), x => x < 3).toArray();
// Returns: [3, 1]

// Nothing is dropped once the first element fails the predicate.
dropWhile([5, 1, 2].values(), x => x < 3).toArray();
// Returns: [5, 1, 2]

Parameters

• source (Iterator<T>): The iterator to drop elements from.
• shouldDrop ((value: T, index: number) => boolean): Called with each element and its index; elements are skipped while it returns a truthy value.

Returns

(IteratorObject<T, undefined>): A lazy iterator over the elements after the dropped leading run. It carries every native iterator helper (map, take, toArray, ...) for further chaining.