Invoke a function for each element in a collection.
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var forEach = require( '@stdlib/utils-for-each' );Invokes a function for each element in a collection.
function log( value, index ) {
console.log( '%s: %d', index, value );
}
var arr = [ 1, 2, 3, 4 ];
forEach( arr, log );
/* =>
0: 1
1: 2
2: 3
3: 4
*/The invoked function is provided three arguments:
value: collection elementindex: collection indexcollection: input collection
Basic support for dynamic collections is provided. Note, however, that index incrementation is monotonically increasing.
function log1( value, index, collection ) {
console.log( '%s: %d', index, value );
if ( index === collection.length-1 && collection.length < 10 ) {
collection.push( index+2 );
}
}
var arr = [ 1, 2, 3, 4 ];
forEach( arr, log1 );
/* =>
0: 1
1: 2
2: 3
3: 4
4: 5
5: 6
6: 7
7: 8
8: 9
9: 10
*/
function log2( value, index, collection ) {
console.log( '%s: %d', index, value );
collection.shift();
}
arr = [ 1, 2, 3, 4 ];
forEach( arr, log2 );
/* =>
0: 1
1: 3
*/To set the function execution context, provide a thisArg.
function sum( value ) {
this.sum += value;
this.count += 1;
}
var arr = [ 1, 2, 3, 4 ];
var context = {
'sum': 0,
'count': 0
};
forEach( arr, sum, context );
var mean = context.sum / context.count;
// returns 2.5-
A
collectionmay be either anArray,Typed Array, or an array-likeObject(excludingstringsandfunctions). -
The function differs from
Array.prototype.forEachin the following ways:-
The function returns the input
collection. -
The function does not skip
undefinedelements.function log( value, index ) { console.log( '%s: %s', index, value ); } var arr = [ 1, , , 4 ]; forEach( arr, log ); /* => 0: 1 1: undefined 2: undefined 3: 4 */
-
The function provides limited support for dynamic collections (i.e., collections whose
lengthchanges during execution).
-
var isEven = require( '@stdlib/assert-is-even' ).isPrimitive;
var forEach = require( '@stdlib/utils-for-each' );
function log( value, index, collection ) {
console.log( '%s: %d', index, value );
if ( isEven( index ) ) {
collection.shift();
} else {
collection.push( index+1 );
}
}
var arr;
var i;
arr = new Array( 100 );
for ( i = 0; i < arr.length; i++ ) {
arr[ i ] = i;
}
forEach( arr, log );@stdlib/utils/async/for-each: invoke a function once for each element in a collection.@stdlib/utils/for-each-right: invoke a function for each element in a collection, iterating from right to left.
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 © 2016-2023. The Stdlib Authors.
