@stdlib/utils-inmap-right v0.2.1
inmapRight
Invoke a function for each element in a collection and update the collection in-place, iterating from right to left.
Installation
npm install @stdlib/utils-inmap-right
Usage
var inmapRight = require( '@stdlib/utils-inmap-right' );
inmapRight( collection, fcn[, thisArg ] )
Invokes a function
for each element in a collection
and updates the collection
in-place, iterating from right to left.
function scale( value, index ) {
return value * index;
}
var arr = [ 1, 2, 3, 4 ];
var out = inmapRight( arr, scale );
// returns [ 0, 2, 6, 12 ]
var bool = ( out === arr );
// returns true
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 not guaranteed to be monotonically decreasing.
var arr = [ 1, 2, 3, 4 ];
var i = 0;
function scale1( value, index, collection ) {
i += 1;
if ( index === 0 && collection.length < 10 ) {
collection.unshift( i+1 );
}
return value * index;
}
var out = inmapRight( arr, scale1 );
// returns [ 0, 0, 0, 0, 0, 0, 0, 2, 6, 12 ]
function scale2( value, index, collection ) {
collection.shift();
return value * index;
}
arr = [ 1, 2, 3, 4 ];
out = inmapRight( arr, scale2 );
// returns [ 3, 12 ]
To set the function execution context, provide a thisArg
.
function sum( value ) {
this.sum += value;
this.count += 1;
return value;
}
var arr = [ 1, 2, 3, 4 ];
var context = {
'sum': 0,
'count': 0
};
var out = inmapRight( arr, sum, context );
// returns [ 1, 2, 3, 4 ]
var mean = context.sum / context.count;
// returns 2.5
Notes
A
collection
may be either anArray
,Typed Array
, or an array-likeObject
(excludingstrings
andfunctions
).The function differs from
Array.prototype.map
in the following ways:The function returns the input
collection
.The function modifies
collection
elements in-place.The function does not skip
undefined
elements.function log( value, index ) { console.log( '%s: %s', index, value ); return value; } var arr = [ 1, , , 4 ]; var out = inmapRight( arr, 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).
Examples
var isEven = require( '@stdlib/assert-is-even' ).isPrimitive;
var inmapRight = require( '@stdlib/utils-inmap-right' );
var bool;
var arr;
var out;
var i;
function scale( value, index, collection ) {
i += 1;
if ( isEven( i ) ) {
collection.pop();
} else {
collection.unshift( i+1 );
}
return value * index;
}
arr = new Array( 100 );
for ( i = 0; i < arr.length; i++ ) {
arr[ i ] = i;
}
i = 0;
out = inmapRight( arr, scale );
bool = ( out === arr );
console.log( bool );
console.log( out );
See Also
@stdlib/utils-for-each-right
: invoke a function for each element in a collection, iterating from right to left.@stdlib/utils-inmap
: invoke a function for each element in a collection and update the collection in-place.@stdlib/utils-map-right
: apply a function to each element in an array and assign the result to an element in an output array, 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.