filterAsync

The async counterpart to Array.prototype.filter: runs predicate for every item and resolves to the items whose predicate was truthy, in their original relative order.

predicate runs for every item up front (respecting concurrency) before any filtering happens — unlike the sync .filter(), there’s no short-circuiting, since every predicate call may already be in flight by the time an earlier one resolves.

Available since v3.0.4

Import

import { filterAsync } from '@helpers4/array';
// or, from the all-in-one package (same code, one install):
import { filterAsync } from 'helpers4/array';

Signature

filterAsync<T>(array: readonly T[], predicate: function, concurrency?: number): Promise<T[]>

Parameters

Parameter	Type	Description
array	readonly T[]	The array to filter
predicate	function	Async (or sync) predicate called with `(item, index)`
concurrency	number	Maximum number of concurrent predicate calls. Defaults to unlimited. (optional)

Returns

Promise<T[]> — The items whose predicate resolved truthy, in original order

Examples

Keep only the files that pass an async check

Every predicate call runs concurrently; matches keep their original order.

await filterAsync(files, (file) => fileExists(file))
// => only the files that actually exist

Source

View source on GitHub