@stdlib/utils-async-parallel
v0.1.0
Published
Execute a set of functions in parallel.
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parallel
Execute functions in parallel and pass the results of all functions to a provided callback.
Installation
npm install @stdlib/utils-async-parallel
Usage
var parallel = require( '@stdlib/utils-async-parallel' );
parallel( fcns, [options,] done )
Executes a set of functions in parallel and passes the results of all functions to a provided callback.
function a( clbk ) {
setTimeout( onTimeout, 0 );
function onTimeout() {
clbk( null, 2 );
}
}
function b( clbk ) {
setTimeout( onTimeout, 0 );
function onTimeout() {
clbk( null, 4 );
}
}
function done( error, out ) {
if ( error ) {
throw error;
}
console.log( out );
// => [ 2, 4 ]
}
var fcns = [ a, b ];
parallel( fcns, done );
The function accepts the following options
:
- 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 the limit
option.
function a( clbk ) {
setTimeout( onTimeout, 0 );
function onTimeout() {
clbk( null, 2 );
}
}
function b( clbk ) {
setTimeout( onTimeout, 0 );
function onTimeout() {
clbk( null, 4 );
}
}
function done( error, out ) {
if ( error ) {
throw error;
}
console.log( out );
// => [ 2, 4 ]
}
var fcns = [ a, b ];
var opts = {
'limit': 1
};
parallel( fcns, opts, done );
To set the this
context for all functions
in the provided function array, set the thisArg
option.
function a( clbk ) {
this.idx += 1;
clbk( null, 2 );
}
function b( clbk ) {
this.idx += 1;
clbk( null, 4 );
}
var fcns = [ a, b ];
var ctx = {
'idx': 0
};
var opts = {
'thisArg': ctx
};
parallel( fcns, opts, done );
function done( error, out ) {
if ( error ) {
throw error;
}
console.log( ctx.idx );
// => 2
}
parallel.factory( fcns, [options] )
Returns a reusable function which executes a set of functions in parallel.
function a( clbk ) {
setTimeout( onTimeout, 0 );
function onTimeout() {
clbk( null, 2 );
}
}
function b( clbk ) {
setTimeout( onTimeout, 0 );
function onTimeout() {
clbk( null, 4 );
}
}
function done( error, out ) {
if ( error ) {
throw error;
}
console.log( out );
// => [ 2, 4 ]
}
var fcns = [ a, b ];
var run = parallel.factory( fcns );
run( done );
run( done );
run( done );
Notes
- The order of the results provided to the
done
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 an
error
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, the
done
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 does not guarantee that execution is asynchronous. To do so, wrap the
done
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 does not spawn new threads.
Examples
var parallel = require( '@stdlib/utils-async-parallel' );
function foo( clbk ) {
setTimeout( onTimeout, 300 );
function onTimeout() {
clbk( null, 'one' );
}
}
function bar( clbk ) {
setTimeout( onTimeout, 100 );
function onTimeout() {
clbk( null, 'two' );
}
}
function done( error, results ) {
if ( error ) {
throw error;
}
console.log( results );
// => [ 'one', 'two' ]
}
var fcns = [ foo, bar ];
parallel( fcns, done );
Notice
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.
Community
License
See LICENSE.
Copyright
Copyright © 2016-2024. The Stdlib Authors.