flatMapAsync

⚡ Asynchronous version of `Array.prototype.flatMap`.

Info

By default, it runs all iterations in parallel. You can limit the concurrency through an options object.

Syntax

TypeScript

import { flatMapAsync } from '@opentf/std';
flatMapAsync<T, R>(
  arr: T[],
  cb: (value: T, index: number) => Promise<R | R[]>,
  options?: { concurrency?: number }
): Promise<R[]>;

Parameters

arr: The array to iterate over.
cb: An async callback function for each element.
options.concurrency (Optional): The maximum number of concurrent executions. Default: Infinity.

Returns

A Promise that resolves to the flattened mapped array.

Sparse array holes are skipped, matching native Array.prototype.flatMap() behavior.

Examples

TypeScript

const items = [1, 2, 3];
const result = await flatMapAsync(items, async (n) => {
  return [n, n * 2];
}); //=> [1, 2, 2, 4, 3, 6]

const limited = await flatMapAsync(items, async (n) => [n, n * 2], {
  concurrency: 2,
}); //=> [1, 2, 2, 4, 3, 6]

Try it

Last updated on September 30, 2026