npm install @stdlib/utils-async-parallel

Alternatively,

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• For use in Observable, or in browser/node environments, use theUniversal Module Definition (UMD) build available on theumd branch (seeREADME).

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varparallel=require('@stdlib/utils-async-parallel');

Executes a set of functions in parallel and passes the results of all functions to a provided callback.

functiona(clbk){setTimeout(onTimeout,0);functiononTimeout(){clbk(null,2);}}functionb(clbk){setTimeout(onTimeout,0);functiononTimeout(){clbk(null,4);}}functiondone(error,out){if(error){throwerror;}console.log(out);// => [ 2, 4 ]}varfcns=[a,b];parallel(fcns,done);

The function accepts the followingoptions:

• limit: maximum number of functions to execute concurrently. Default:infinity.
• thisArg: execution context for each function.

To limit the maximum number of functions executing in parallel, set thelimit option.

functiona(clbk){setTimeout(onTimeout,0);functiononTimeout(){clbk(null,2);}}functionb(clbk){setTimeout(onTimeout,0);functiononTimeout(){clbk(null,4);}}functiondone(error,out){if(error){throwerror;}console.log(out);// => [ 2, 4 ]}varfcns=[a,b];varopts={'limit':1};parallel(fcns,opts,done);

To set thethis context forallfunctions in the provided function array, set thethisArg option.

functiona(clbk){this.idx+=1;clbk(null,2);}functionb(clbk){this.idx+=1;clbk(null,4);}varfcns=[a,b];varctx={'idx':0};varopts={'thisArg':ctx};parallel(fcns,opts,done);functiondone(error,out){if(error){throwerror;}console.log(ctx.idx);// => 2}

Returns a reusable function which executes a set of functions in parallel.

functiona(clbk){setTimeout(onTimeout,0);functiononTimeout(){clbk(null,2);}}functionb(clbk){setTimeout(onTimeout,0);functiononTimeout(){clbk(null,4);}}functiondone(error,out){if(error){throwerror;}console.log(out);// => [ 2, 4 ]}varfcns=[a,b];varrun=parallel.factory(fcns);run(done);run(done);run(done);

• The order of the results provided to thedone callback corresponds to the order of the provided functions.
• When executed, each provided function is invoked with a single callback argument. The callback should be invoked upon function completion. The first argument is reserved as anerror argument (which can benull). The second argument is reserved for any results which should be passed to thedone callback upon completion of all provided functions.
• If any function fails to invoke the callback argument, thedone callback will never be invoked.
• This implementation is intended to start asynchronous tasks so that execution of each task runs concurrently. If provided a function which does not perform asynchronous tasks, the function will execute synchronously. Hence, this implementation doesnot guarantee that execution is asynchronous. To do so, wrap thedone callback in afunction 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).
• The function executes provided functions in the same thread. Accordingly, the function doesnot spawn new threads.

This package is part ofstdlib, 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 developstdlib, see the main projectrepository.

SeeLICENSE.

Copyright © 2016-2025. The StdlibAuthors.