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https://github.com/stdlib-js/utils-until-each

Until a test condition is true, invoke a function for each element in a collection.
https://github.com/stdlib-js/utils-until-each

array array-like collection each for foreach iterate javascript node node-js nodejs stdlib typed-array until util utilities utility utils while

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Until a test condition is true, invoke a function for each element in a collection.

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README 

        



  

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# untilEach



[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url] 



> Until a test condition is true, invoke a function for each element in a collection.



## Installation



```bash

npm install @stdlib/utils-until-each

```



Alternatively,



-   To load the package in a website via a `script` tag without installation and bundlers, use the [ES Module][es-module] available on the [`esm`][esm-url] branch (see [README][esm-readme]).

-   If you are using Deno, visit the [`deno`][deno-url] branch (see [README][deno-readme] for usage intructions).

-   For use in Observable, or in browser/node environments, use the [Universal Module Definition (UMD)][umd] build available on the [`umd`][umd-url] branch (see [README][umd-readme]).



The [branches.md][branches-url] file summarizes the available branches and displays a diagram illustrating their relationships.



To view installation and usage instructions specific to each branch build, be sure to explicitly navigate to the respective README files on each branch, as linked to above.



## Usage



```javascript

var untilEach = require( '@stdlib/utils-until-each' );

```



#### untilEach( collection, predicate, fcn\[, thisArg ] )



Invokes a `function` for each element in a `collection` until either a `predicate` function returns `true` or the function has iterated over all `collection` elements.



```javascript

function predicate( value ) {

    return ( value !== value );

}



function log( value, index ) {

    console.log( '%s: %d', index, value );

}



var arr = [ 1, 2, 3, NaN, 4 ];



untilEach( arr, predicate, log );

/* =>

    0: 1

    1: 2

    2: 3

*/

```



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 monotonically increasing.



```javascript

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 ];



untilEach( 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 ];



untilEach( arr, predicate, log2 );

/* =>

    0: 1

    1: 3

*/

```



To set the function execution context for the applied function, provide a `thisArg`.



```javascript

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

};



untilEach( arr, predicate, sum, context );



var mean = context.sum / context.count;

// returns 2.0

```



## Notes



-   A `collection` may be either an [`Array`][mdn-array], [`Typed Array`][mdn-typed-array], or an array-like [`Object`][mdn-object] (excluding `strings` and `functions`).



-   The function returns the input `collection`.



-   The function does **not** skip `undefined` elements.



    



    ```javascript

    function predicate( value ) {

        return ( value !== value );

    }



    function log( value, index ) {

        console.log( '%s: %s', index, value );

    }



    var arr = [ 1, , , 4 ];



    untilEach( 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



```javascript

var isEven = require( '@stdlib/assert-is-even' ).isPrimitive;

var randu = require( '@stdlib/random-base-randu' );

var floor = require( '@stdlib/math-base-special-floor' );

var untilEach = require( '@stdlib/utils-until-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;

    }

}



untilEach( arr, predicate, log );

```



* * *



## See Also



-   [`@stdlib/utils-until-each-right`][@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.

-   [`@stdlib/utils-while-each`][@stdlib/utils/while-each]: while a test condition is true, invoke a function for each element in a collection.



* * *



## Notice



This package is part of [stdlib][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][stdlib], see the main project [repository][stdlib].



#### Community



[![Chat][chat-image]][chat-url]



---



## License



See [LICENSE][stdlib-license].



## Copyright



Copyright © 2016-2024. The Stdlib [Authors][stdlib-authors].



[npm-image]: http://img.shields.io/npm/v/@stdlib/utils-until-each.svg

[npm-url]: https://npmjs.org/package/@stdlib/utils-until-each



[test-image]: https://github.com/stdlib-js/utils-until-each/actions/workflows/test.yml/badge.svg?branch=main

[test-url]: https://github.com/stdlib-js/utils-until-each/actions/workflows/test.yml?query=branch:main



[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/utils-until-each/main.svg

[coverage-url]: https://codecov.io/github/stdlib-js/utils-until-each?branch=main



[chat-image]: https://img.shields.io/gitter/room/stdlib-js/stdlib.svg

[chat-url]: https://app.gitter.im/#/room/#stdlib-js_stdlib:gitter.im



[stdlib]: https://github.com/stdlib-js/stdlib



[stdlib-authors]: https://github.com/stdlib-js/stdlib/graphs/contributors



[umd]: https://github.com/umdjs/umd

[es-module]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Modules



[deno-url]: https://github.com/stdlib-js/utils-until-each/tree/deno

[deno-readme]: https://github.com/stdlib-js/utils-until-each/blob/deno/README.md

[umd-url]: https://github.com/stdlib-js/utils-until-each/tree/umd

[umd-readme]: https://github.com/stdlib-js/utils-until-each/blob/umd/README.md

[esm-url]: https://github.com/stdlib-js/utils-until-each/tree/esm

[esm-readme]: https://github.com/stdlib-js/utils-until-each/blob/esm/README.md

[branches-url]: https://github.com/stdlib-js/utils-until-each/blob/main/branches.md



[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/utils-until-each/main/LICENSE



[mdn-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array



[mdn-typed-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray



[mdn-object]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object



[@stdlib/utils/until-each-right]: https://github.com/stdlib-js/utils-until-each-right



[@stdlib/utils/while-each]: https://github.com/stdlib-js/utils-while-each