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Invoke a function
ntimes and return an array of accumulated function return values.
npm install @stdlib/utils-async-map-functionAlternatively,
- To load the package in a website via a
scripttag without installation and bundlers, use the ES Module available on theesmbranch (see README). - If you are using Deno, visit the
denobranch (see README for usage intructions). - For use in Observable, or in browser/node environments, use the Universal Module Definition (UMD) build available on the
umdbranch (see README).
The branches.md file summarizes the available branches and displays a diagram illustrating their relationships.
To view installation and usage instructions specific to each branch build, be sure to explicitly navigate to the respective README files on each branch, as linked to above.
var mapFunAsync = require( '@stdlib/utils-async-map-function' );Invokes a function n times and returns an array of accumulated function return values.
function fcn( i, next ) {
var t = 300 - (i*50);
setTimeout( onTimeout, t );
function onTimeout() {
console.log( i );
next( null, i );
}
}
function done( error, arr ) {
if ( error ) {
throw error;
}
console.log( arr );
}
mapFunAsync( fcn, 5, done );
/* =>
4
3
2
1
0
[ 0, 1, 2, 3, 4 ]
*/For each iteration, the provided function is invoked with two arguments:
index: invocation index (starting from zero).next: callback to be invoked upon function completion.
The next callback accepts two arguments:
error: error argument.result: function result.
The function accepts the following options:
limit: the maximum number of pending invocations at any one time. Default:infinity.series:booleanindicating whether to sequentially invokefcn. Iftrue, the function setsoptions.limit=1. Default:false.thisArg: the execution context forfcn.
By default, all invocations are performed concurrently, which means that the function does not guarantee completion order. To invoke a function such that only one invocation is pending at any one time, set the series option to true.
function fcn( i, next ) {
var t = 300 - (i*50);
setTimeout( onTimeout, t );
function onTimeout() {
console.log( i );
next( null, i );
}
}
function done( error, arr ) {
if ( error ) {
throw error;
}
console.log( arr );
}
var opts = {
'series': true
};
mapFunAsync( fcn, 5, opts, done );
/* =>
0
1
2
3
4
[ 0, 1, 2, 3, 4 ]
*/To limit the maximum number of pending function invocations, set the limit option.
var delays = [ 300, 250, 225, 150, 100 ];
function fcn( i, next ) {
setTimeout( onTimeout, delays[ i ] );
function onTimeout() {
console.log( i );
next( null, i );
}
}
function done( error, arr ) {
if ( error ) {
throw error;
}
console.log( arr );
}
var opts = {
'limit': 2
};
mapFunAsync( fcn, 5, opts, done );
/* =>
1
0
3
2
4
[ 0, 1, 2, 3, 4 ]
*/To set the execution context of fcn, set the thisArg option.
function fcn( i, next ) {
this.count += 1;
setTimeout( onTimeout, 0 );
function onTimeout() {
next( null, i );
}
}
function done( error, arr ) {
if ( error ) {
throw error;
}
console.log( arr );
// => [ 0, 1, 2, 3, 4 ]
}
var ctx = {
'count': 0
};
var opts = {
'thisArg': ctx
};
mapFunAsync( fcn, 5, opts, done );Returns a function which invokes a function n times and returns an array of accumulated function return values.
function fcn( i, next ) {
var t = 300 - (i*50);
setTimeout( onTimeout, t );
function onTimeout() {
console.log( i );
next( null, i );
}
}
function done( error, arr ) {
if ( error ) {
throw error;
}
console.log( arr );
}
var opts = {
'series': true
};
var f = mapFunAsync.factory( opts, fcn );
f( 5, done );
/* =>
0
1
2
3
4
[ 0, 1, 2, 3, 4 ]
*/
f( 2, done );
/* =>
0
1
[ 0, 1 ]
*/The function accepts the same options as mapFunAsync().
- If a provided function calls the
nextcallback with a truthyerrorargument, the function suspends execution and immediately calls thedonecallback for subsequenterrorhandling. - Neither
mapFunAsyncnor the function returned by thefactorymethod guarantee asynchronous execution. To guarantee asynchrony, wrap thedonecallback in a function which either executes at the end of the current stack (e.g.,nextTick) or during a subsequent turn of the event loop (e.g.,setImmediate,setTimeout).
var randu = require( '@stdlib/random-base-randu' );
var mapFunAsync = require( '@stdlib/utils-async-map-function' );
function rand( i, next ) {
var t = randu() * i;
setTimeout( onTimeout, t );
function onTimeout() {
next( null, t );
}
}
function done( error, out ) {
if ( error ) {
throw error;
}
console.log( out );
}
mapFunAsync( rand, 10, done );@stdlib/utils-map-function: invoke a function n times and return an array of accumulated function return values.
This package is part of stdlib, a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.
For more information on the project, filing bug reports and feature requests, and guidance on how to develop stdlib, see the main project repository.
See LICENSE.
Copyright © 2016-2025. The Stdlib Authors.
