@stdlib/utils-while-each
v0.2.2
Published
While a test condition is true, invoke a function for each element in a collection.
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whileEach
While a test condition is true, invoke a function for each element in a collection.
Installation
npm install @stdlib/utils-while-each
Usage
var whileEach = require( '@stdlib/utils-while-each' );
whileEach( collection, predicate, fcn[, thisArg ] )
Invokes a function
for each element in a collection
until either a predicate
function returns false
or the function has iterated over all collection
elements.
function predicate( value ) {
return ( value === value );
}
function log( value, index ) {
console.log( '%s: %d', index, value );
}
var arr = [ 1, 2, 3, NaN, 4 ];
whileEach( arr, predicate, log );
/* =>
0: 1
1: 2
2: 3
*/
Both the predicate
function and the function
to apply are 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 predicate( value ) {
return ( value === value );
}
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 ];
whileEach( arr, predicate, 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 ];
whileEach( arr, predicate, log2 );
/* =>
0: 1
1: 3
*/
To set the function execution context for the applied function, provide a thisArg
.
function predicate( value ) {
return ( value === value );
}
function sum( value ) {
this.sum += value;
this.count += 1;
}
var arr = [ 1, 2, 3, NaN, 4 ];
var context = {
'sum': 0,
'count': 0
};
whileEach( arr, predicate, sum, context );
var mean = context.sum / context.count;
// returns 2.0
Notes
A
collection
may be either anArray
,Typed Array
, or an array-likeObject
(excludingstrings
andfunctions
).The function returns the input
collection
.The function does not skip
undefined
elements.function predicate( value ) { return ( value === value ); } function log( value, index ) { console.log( '%s: %s', index, value ); } var arr = [ 1, , , 4 ]; whileEach( arr, predicate, log ); /* => 0: 1 1: undefined 2: undefined 3: 4 */
The function provides limited support for dynamic collections (i.e., collections whose
length
changes during execution).
Examples
var isEven = require( '@stdlib/assert-is-even' ).isPrimitive;
var randu = require( '@stdlib/random-base-randu' );
var floor = require( '@stdlib/math-base-special-floor' );
var whileEach = require( '@stdlib/utils-while-each' );
function predicate( value ) {
return ( value === value );
}
function log( value, index, collection ) {
console.log( '%s: %d', index, value );
if ( isEven( index ) ) {
collection.shift();
} else {
collection.push( index+1 );
}
}
var arr;
var j;
var i;
arr = new Array( 100 );
j = floor( randu()*arr.length );
for ( i = 0; i < arr.length; i++ ) {
if ( i === j ) {
arr[ i ] = NaN;
} else {
arr[ i ] = i;
}
}
whileEach( arr, predicate, log );
See Also
@stdlib/utils-until-each
: until a test condition is true, invoke a function for each element in a collection.@stdlib/utils-while-each-right
: while a test condition is true, invoke a function for each element in a collection, iterating from right to left.
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.