npm package: @stdlib/iter-to-array-view
Description: Fill an array-like object view with values returned from an iterator.
Author: The Stdlib Authors
Latest version: 0.2.3

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<details>
  <summary>
    About stdlib...
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# iterator2arrayview

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

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

<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->

<section class="intro">

</section>

<!-- /.intro -->

<!-- Package usage documentation. -->

<section class="installation">

## Installation

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

</section>

<section class="usage">

## 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 <Uint8Array>[ 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 <Uint8Array>[ 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 <Uint8Array>[ 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 <Uint8Array>[ 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 <Uint8Array>[ 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 <Float64Array>[ 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 <Uint8Array>[ 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 <Float64Array>

var count = ctx.count;
// returns 10
```

</section>

<!-- /.usage -->

<!-- Package usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="notes">

## 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]).

</section>

<!-- /.notes -->

<!-- Package usage examples. -->

<section class="examples">

## Examples

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

```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 ] );
}
```

</section>

<!-- /.examples -->

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<section class="references">

</section>

<!-- /.references -->

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

<section class="related">

* * *

## See Also

-   <span class="package-name">[`@stdlib/array-from-iterator`][@stdlib/array/from-iterator]</span><span class="delimiter">: </span><span class="description">create (or fill) an array from an iterator.</span>
-   <span class="package-name">[`@stdlib/array-to-view-iterator`][@stdlib/array/to-view-iterator]</span><span class="delimiter">: </span><span class="description">create an iterator from an array-like object view.</span>
-   <span class="package-name">[`@stdlib/iter-to-array-view-right`][@stdlib/iter/to-array-view-right]</span><span class="delimiter">: </span><span class="description">fill an array-like object view from right to left with values returned from an iterator.</span>

</section>

<!-- /.related -->

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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

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---

## License

See [LICENSE][stdlib-license].


## Copyright

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

</section>

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[@stdlib/array/complex64]: https://www.npmjs.com/package/@stdlib/array-complex64

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