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https://github.com/stdlib-js/array-base-mskreject-map

Apply a mask to a provided input array and map the unmasked values according to a callback function.
https://github.com/stdlib-js/array-base-mskreject-map

array copy extract filter generic index javascript mask node node-js nodejs reject stdlib take utilities utils

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Apply a mask to a provided input array and map the unmasked values according to a callback function.

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README 

        



  

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# mskrejectMap



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



> Apply a mask to a provided input array and map the unmasked values according to a callback function.



## Installation



```bash

npm install @stdlib/array-base-mskreject-map

```



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 mskrejectMap = require( '@stdlib/array-base-mskreject-map' );

```



#### mskrejectMap( x, mask, clbk\[, thisArg ] )



Returns a new array by applying a mask and mapping the unmasked values according to a callback function.



```javascript

var x = [ 1, 2, 3, 4 ];



function clbk( val ) {

    return val * 2;

}



var y = mskrejectMap( x, [ 0, 1, 0, 1 ], clbk );

// returns [ 2, 6 ]

```



The function supports the following parameters:



-   **x**: input array.

-   **mask**: mask array.

-   **clbk**: function to apply.

-   **thisArg**: applied function execution context (_optional_).



The `clbk` function is provided three arguments:



-   **value**: current unmasked array element.

-   **index**: current unmasked array element index.

-   **arr**: input array.



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



```javascript

var x = [ 1, 2, 3, 4 ];



var mask = [ 0, 1, 0, 1 ];



var increase = 3;



function clbk( value ) {

    return value + this;

}



var out = mskrejectMap( x, mask, clbk, increase );

// returns [ 4, 6 ]

```



The function **always** returns a new "generic" array.



#### mskrejectMap.assign( x, mask, out, stride, offset, clbk\[, thisArg ] )



Applies a mask to a provided input array, maps the unmasked values according to a callback function, and assigns to elements in a provided output array.



```javascript

var x = [ 1, 2, 3, 4 ];



var mask = [ 1, 0, 1, 0 ];



var out = [ 0, 0, 0, 0 ];



function clbk( val ) {

    return val * 2;

}



var arr = mskrejectMap.assign( x, mask, out, -2, out.length-1, clbk );

// returns [ 0, 8, 0, 4 ]



var bool = ( arr === out );

// returns true

```



The function supports the following parameters:



-   **x**: input array.

-   **mask**: mask array.

-   **out**: output array.

-   **stride**: output array stride.

-   **offset**: output array offset.

-   **clbk**: function to apply.

-   **thisArg**: applied function execution context (_optional_).



## Notes



-   If a `mask` array element is falsy, the corresponding element in `x` is **mapped** in the output array; otherwise, the corresponding element in `x` is "masked" and thus **excluded** from the output array.



## Examples



```javascript

var zeroTo = require( '@stdlib/array-base-zero-to' );

var bernoulli = require( '@stdlib/random-array-bernoulli' );

var mskrejectMap = require( '@stdlib/array-base-mskreject-map' );



// Generate a linearly spaced array:

var x = zeroTo( 20 );

console.log( x );



// Generate a random mask:

var mask = bernoulli( x.length, 0.5, {

    'dtype': 'generic'

});

console.log( mask );



function clbk( val ) {

    return val * 2;

}



// Filter an array using the mask:

var y = mskrejectMap( x, mask, clbk );

console.log( y );

```



* * *



## 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/array-base-mskreject-map.svg

[npm-url]: https://npmjs.org/package/@stdlib/array-base-mskreject-map



[test-image]: https://github.com/stdlib-js/array-base-mskreject-map/actions/workflows/test.yml/badge.svg?branch=main

[test-url]: https://github.com/stdlib-js/array-base-mskreject-map/actions/workflows/test.yml?query=branch:main



[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/array-base-mskreject-map/main.svg

[coverage-url]: https://codecov.io/github/stdlib-js/array-base-mskreject-map?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/array-base-mskreject-map/tree/deno

[deno-readme]: https://github.com/stdlib-js/array-base-mskreject-map/blob/deno/README.md

[umd-url]: https://github.com/stdlib-js/array-base-mskreject-map/tree/umd

[umd-readme]: https://github.com/stdlib-js/array-base-mskreject-map/blob/umd/README.md

[esm-url]: https://github.com/stdlib-js/array-base-mskreject-map/tree/esm

[esm-readme]: https://github.com/stdlib-js/array-base-mskreject-map/blob/esm/README.md

[branches-url]: https://github.com/stdlib-js/array-base-mskreject-map/blob/main/branches.md



[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/array-base-mskreject-map/main/LICENSE