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https://github.com/stdlib-js/iter-to-array-view

Fill an array-like object view with values returned from an iterator.
https://github.com/stdlib-js/iter-to-array-view

arr array array-like iter iterate iteration iterator javascript node node-js nodejs stdlib to typed typed-array util utilities utility utils

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Fill an array-like object view with values returned from an iterator.

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README 

        



  

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# iterator2arrayview



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



> Fill an array-like object view with values returned from an iterator.



## Installation



```bash

npm install @stdlib/iter-to-array-view

```



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 iterator2arrayview = require( '@stdlib/iter-to-array-view' );

```



#### iterator2arrayview( iterator, dest\[, begin\[, end]]\[, mapFcn\[, thisArg]] )



Fills an array-like `object` view with values returned from an `iterator`.



```javascript

var Uint8Array = require( '@stdlib/array-uint8' );

var array2iterator = require( '@stdlib/array-to-iterator' );



var iter = array2iterator( [ 1, 2, 3, 4 ] );



var arr = iterator2arrayview( iter, new Uint8Array( 10 ) );

// returns [ 1, 2, 3, 4, 0, 0, 0, 0, 0, 0 ]

```



By default, the function begins filling from the first element of a provided array-like `object`. To specify an alternative starting index, provide a `begin` argument (zero-based and inclusive).



```javascript

var Uint8Array = require( '@stdlib/array-uint8' );

var array2iterator = require( '@stdlib/array-to-iterator' );



var iter = array2iterator( [ 1, 2, 3, 4 ] );



var arr = iterator2arrayview( iter, new Uint8Array( 10 ), 3 );

// returns [ 0, 0, 0, 1, 2, 3, 4, 0, 0, 0 ]

```



If `begin` is less than `0`, the starting index is resolved relative to the last element of the provided array-like `object`. For example, the following achieves the same behavior as the previous example



```javascript

var Uint8Array = require( '@stdlib/array-uint8' );

var array2iterator = require( '@stdlib/array-to-iterator' );



var iter = array2iterator( [ 1, 2, 3, 4 ] );



var arr = iterator2arrayview( iter, new Uint8Array( 10 ), -7 );

// returns [ 0, 0, 0, 1, 2, 3, 4, 0, 0, 0 ]

```



By default, the function assumes that a view extends through the last element of a provided array-like `object`. To specify an alternative last view element, provide an `end` argument (zero-based and non-inclusive).



```javascript

var Uint8Array = require( '@stdlib/array-uint8' );

var array2iterator = require( '@stdlib/array-to-iterator' );



var iter = array2iterator( [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ] );



var arr = iterator2arrayview( iter, new Uint8Array( 10 ), 0, 4 );

// returns [ 1, 2, 3, 4, 0, 0, 0, 0, 0, 0 ]

```



If `end` is less than `0`, the last view element is resolved relative to the last element of the provided array-like `object`. For example, the following achieves the same behavior as the previous example



```javascript

var Uint8Array = require( '@stdlib/array-uint8' );

var array2iterator = require( '@stdlib/array-to-iterator' );



var iter = array2iterator( [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ] );



var arr = iterator2arrayview( iter, new Uint8Array( 10 ), 0, -6 );

// returns [ 1, 2, 3, 4, 0, 0, 0, 0, 0, 0 ]

```



To invoke a function for each iterated value, provide a callback function.



```javascript

var Float64Array = require( '@stdlib/array-float64' );

var array2iterator = require( '@stdlib/array-to-iterator' );



function fcn( v ) {

    return v * 10.0;

}



var iter = array2iterator( [ 1, 2, 3, 4 ] );



var arr = iterator2arrayview( iter, new Float64Array( 4 ), fcn );

// returns [ 10.0, 20.0, 30.0, 40.0 ]

```



The invoked function is provided three arguments:



-   **value**: iterated value.

-   **index**: destination index.

-   **n**: iteration count (zero-based).



```javascript

var Uint8Array = require( '@stdlib/array-uint8' );

var array2iterator = require( '@stdlib/array-to-iterator' );



function fcn( v, i ) {

    return v * (i+1);

}



var iter = array2iterator( [ 1, 2, 3, 4 ] );



var arr = iterator2arrayview( iter, new Uint8Array( 4 ), fcn );

// returns [ 1, 4, 9, 16 ]

```



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



```javascript

var Float64Array = require( '@stdlib/array-float64' );

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



function fcn( v ) {

    this.count += 1;

    return v * 10.0;

}



var ctx = {

    'count': 0

};



var arr = iterator2arrayview( randu(), new Float64Array( 10 ), fcn, ctx );

// returns 



var count = ctx.count;

// returns 10

```



## Notes



-   Iteration stops when an output array view is full **or** an iterator finishes; whichever comes first.

-   The function supports output array-like objects having getter and setter accessors for array element access (e.g., [`@stdlib/array-complex64`][@stdlib/array/complex64]).



## Examples



```javascript

var Float64Array = require( '@stdlib/array-float64' );

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

var iterator2arrayview = require( '@stdlib/iter-to-array-view' );



function scale( v, i ) {

    return v * (i+1);

}



// Create an iterator for generating uniformly distributed pseudorandom numbers:

var it = randu();



// Fill an array view with scaled iterator values:

var arr = iterator2arrayview( it, new Float64Array( 100 ), 40, 60, scale );



var i;

for ( i = 0; i < arr.length; i++ ) {

    console.log( arr[ i ] );

}

```



* * *



## See Also



-   [`@stdlib/array-from-iterator`][@stdlib/array/from-iterator]: create (or fill) an array from an iterator.

-   [`@stdlib/array-to-view-iterator`][@stdlib/array/to-view-iterator]: create an iterator from an array-like object view.

-   [`@stdlib/iter-to-array-view-right`][@stdlib/iter/to-array-view-right]: fill an array-like object view from right to left with values returned from an iterator.



* * *



## 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/iter-to-array-view.svg

[npm-url]: https://npmjs.org/package/@stdlib/iter-to-array-view



[test-image]: https://github.com/stdlib-js/iter-to-array-view/actions/workflows/test.yml/badge.svg?branch=main

[test-url]: https://github.com/stdlib-js/iter-to-array-view/actions/workflows/test.yml?query=branch:main



[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/iter-to-array-view/main.svg

[coverage-url]: https://codecov.io/github/stdlib-js/iter-to-array-view?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/iter-to-array-view/tree/deno

[deno-readme]: https://github.com/stdlib-js/iter-to-array-view/blob/deno/README.md

[umd-url]: https://github.com/stdlib-js/iter-to-array-view/tree/umd

[umd-readme]: https://github.com/stdlib-js/iter-to-array-view/blob/umd/README.md

[esm-url]: https://github.com/stdlib-js/iter-to-array-view/tree/esm

[esm-readme]: https://github.com/stdlib-js/iter-to-array-view/blob/esm/README.md

[branches-url]: https://github.com/stdlib-js/iter-to-array-view/blob/main/branches.md



[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/iter-to-array-view/main/LICENSE



[@stdlib/array/complex64]: https://github.com/stdlib-js/array-complex64



[@stdlib/array/from-iterator]: https://github.com/stdlib-js/array-from-iterator



[@stdlib/array/to-view-iterator]: https://github.com/stdlib-js/array-to-view-iterator



[@stdlib/iter/to-array-view-right]: https://github.com/stdlib-js/iter-to-array-view-right