npm package: @stdlib/array-base-mskreject-map
Description: Apply a mask to a provided input array and map the unmasked values according to a callback function.
Author: The Stdlib Authors
Latest version: 0.0.3

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# mskrejectMap

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

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

<section class="installation">

## Installation

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

</section>

<section class="usage">

## 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_).

</section>

<!-- /.usage -->

<section class="notes">

## 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.

</section>

<!-- /.notes -->

<section class="examples">

## Examples

<!-- eslint no-undef: "error" -->

```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 );
```

</section>

<!-- /.examples -->

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<section class="related">

</section>

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<section class="main-repo" >

* * *

## 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 &copy; 2016-2026. The Stdlib [Authors][stdlib-authors].

</section>

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