Home > @rushstack/node-core-library > Async > mapAsync

Async.mapAsync() method

This API is provided as a preview for developers and may change based on feedback that we receive. Do not use this API in a production environment.

Given an input array and a callback function, invoke the callback to start a promise for each element in the array. Returns an array containing the results.

Signature:

static mapAsync<TEntry, TRetVal>(iterable: Iterable<TEntry> | AsyncIterable<TEntry>, callback: (entry: TEntry, arrayIndex: number) => Promise<TRetVal>, options?: IAsyncParallelismOptions | undefined): Promise<TRetVal[]>;

Parameters

Parameter	Type	Description
iterable	Iterable<TEntry> | AsyncIterable<TEntry>	the array of inputs for the callback function
callback	(entry: TEntry, arrayIndex: number) => Promise<TRetVal>	a function that starts an asynchronous promise for an element from the array
options	IAsyncParallelismOptions | undefined	(Optional) options for customizing the control flow

Returns:

Promise<TRetVal[]>

an array containing the result for each callback, in the same order as the original input array

Remarks

This API is similar to the system Array#map, except that the loop is asynchronous, and the maximum number of concurrent promises can be throttled using IAsyncParallelismOptions.concurrency.

If callback throws a synchronous exception, or if it returns a promise that rejects, then the loop stops immediately. Any remaining array items will be skipped, and overall operation will reject with the first error that was encountered.