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About stdlib...

We believe in a future in which the web is a preferred environment for numerical computation. To help realize this future, we've built stdlib. stdlib is a standard library, with an emphasis on numerical and scientific computation, written in JavaScript (and C) for execution in browsers and in Node.js.

The library is fully decomposable, being architected in such a way that you can swap out and mix and match APIs and functionality to cater to your exact preferences and use cases.

When you use stdlib, you can be absolutely certain that you are using the most thorough, rigorous, well-written, studied, documented, tested, measured, and high-quality code out there.

To join us in bringing numerical computing to the web, get started by checking us out on GitHub, and please consider financially supporting stdlib. We greatly appreciate your continued support!

untilEachRight

NPM version Build Status Coverage Status

Until a test condition is true, invoke a function for each element in a collection, iterating from right to left.

Usage

import untilEachRight from 'https://cdn.jsdelivr.net/gh/stdlib-js/utils-until-each-right@esm/index.mjs';

untilEachRight( collection, predicate, fcn[, thisArg ] )

Invokes a function for each element in a collection, iterating from right to left, until either a predicate function returns true 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 ];

untilEachRight( 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 );
    }
}

untilEachRight( 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 ];

untilEachRight( 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
};

untilEachRight( arr, predicate, sum, context );

var mean = context.sum / context.count;
// returns 3.0

Notes

  • A collection may be either an Array, Typed Array, or an array-like Object (excluding strings and functions).

  • 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 ];

untilEachRight( 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).

Examples

<!DOCTYPE html>
<html lang="en">
<body>
<script type="module">

var isEven = require( 'https://cdn.jsdelivr.net/gh/stdlib-js/assert-is-even' ).isPrimitive;
import randu from 'https://cdn.jsdelivr.net/gh/stdlib-js/random-base-randu@esm/index.mjs';
import floor from 'https://cdn.jsdelivr.net/gh/stdlib-js/math-base-special-floor@esm/index.mjs';
import untilEachRight from 'https://cdn.jsdelivr.net/gh/stdlib-js/utils-until-each-right@esm/index.mjs';

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;
untilEachRight( arr, predicate, log );

</script>
</body>
</html>

See Also

Notice

This package is part of stdlib, a standard library 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

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License

See LICENSE.

Copyright

Copyright © 2016-2024. The Stdlib Authors.