npm package: @stdlib/array-base-mskfilter-map
Description: Apply a mask and a callback function to a provided input array.
Author: The Stdlib Authors
Latest version: 0.1.1

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# mskfilterMap

[![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 and a callback function to a provided input array.

<section class="installation">

## Installation

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

</section>

<section class="usage">

## Usage

```javascript
var mskfilterMap = require( '@stdlib/array-base-mskfilter-map' );
```

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

Returns a new array after applying a mask and a callback function to a provided input array.

```javascript
function clbk( value ) {
    return value * 2;
}

var x = [ 1, 2, 3, 4 ];
var m = [ 0, 1, 0, 1 ];

var y = mskfilterMap( x, m, clbk );
// returns [ 4, 8 ]
```

The function supports the following parameters:

-   **x**: input array.
-   **mask**: mask array.
-   **clbk**: callback to apply.
-   **thisArg**: callback execution context (_optional_).

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

<!-- eslint-disable no-invalid-this -->

```javascript
function clbk( x ) {
    this.count += 1;
    return x;
}

var x = [ 1, 2, 3, 4 ];
var m = [ 1, 1, 0, 1 ];

var ctx = {
    'count': 0
};

var y = mskfilterMap( x, m, clbk, ctx );
// returns [ 1, 2, 4 ]

var v = ctx.count;
// returns 3
```

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

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

Applies a mask and a callback function to a provided input array and assigns results to elements in a provided output array.

```javascript
function clbk( value ) {
    return value * 2;
}

var x = [ 1, 2, 3, 4 ];
var m = [ 0, 1, 0, 1 ];

var out = [ 0, 0, 0, 0 ];
var arr = mskfilterMap.assign( x, m, 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**: callback function.
-   **thisArg**: callback execution context (_optional_).

</section>

<!-- /.usage -->

<section class="notes">

## Notes

-   If a `mask` array element is truthy, the corresponding element in `x` is **included** 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 abs2 = require( '@stdlib/math-base-special-abs2' );
var mskfilterMap = require( '@stdlib/array-base-mskfilter-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 );

// Filter an array using the mask:
var y = mskfilterMap( x, mask, abs2 );
console.log( y );
```

</section>

<!-- /.examples -->

<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->

<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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