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While a test condition is true, invoke a function for each element in a collection, iterating from right to left.
npm install @stdlib/utils-while-each-right
var whileEachRight = require( '@stdlib/utils-while-each-right' );
Invokes a function
for each element in a collection
, iterating from right to left, 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, NaN, 2, 3, 4 ];
whileEachRight( arr, predicate, log );
/* =>
4: 4
3: 3
2: 2
*/
Both the predicate
function and the function
to apply are provided three arguments:
-
value
: collection element -
index
: collection index -
collection
: input collection
Basic support for dynamic collections is provided. Note, however, that index incrementation is not guaranteed to be monotonically decreasing.
var arr = [ 1, 2, 3, 4 ];
var i = 0;
function predicate( value ) {
return ( value === value );
}
function log1( value, index, collection ) {
console.log( '%s: %d', index, value );
i += 1;
if ( index === 0 && collection.length < 10 ) {
collection.unshift( i+1 );
}
}
whileEachRight( arr, predicate, log1 );
/* =>
3: 4
2: 3
1: 2
0: 1
0: 5
0: 6
0: 7
0: 8
0: 9
0: 10
*/
function log2( value, index, collection ) {
console.log( '%s: %d', index, value );
collection.pop();
}
arr = [ 1, 2, 3, 4 ];
whileEachRight( arr, predicate, log2 );
/* =>
3: 4
1: 2
*/
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, NaN, 2, 3, 4 ];
var context = {
'sum': 0,
'count': 0
};
whileEachRight( arr, predicate, sum, context );
var mean = context.sum / context.count;
// returns 3.0
-
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 ]; whileEachRight( arr, predicate, log ); /* => 3: 4 2: undefined 1: undefined 0: 1 */
-
The function provides limited support for dynamic collections (i.e., collections whose
length
changes during execution).
var isEven = require( '@stdlib/assert-is-even' ).isPrimitive;
var randu = require( '@stdlib/random-base-randu' );
var floor = require( '@stdlib/math-base-special-floor' );
var whileEachRight = require( '@stdlib/utils-while-each-right' );
var arr;
var i;
var j;
function predicate( value ) {
return ( value === value );
}
function log( value, index, collection ) {
console.log( '%s: %d', index, value );
i += 1;
if ( isEven( i ) ) {
collection.pop();
} else {
collection.unshift( i+1 );
}
}
arr = new Array( 100 );
j = floor( randu()*arr.length );
for ( i = arr.length-1; i >= 0; i-- ) {
if ( i === j ) {
arr[ i ] = NaN;
} else {
arr[ i ] = i;
}
}
i = 0;
whileEachRight( arr, predicate, log );
-
@stdlib/utils-while-each
: while a test condition is true, invoke a function for each element in a collection. -
@stdlib/utils-until-each-right
: until a test condition is true, 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 © 2016-2024. The Stdlib Authors.