npm package: @stdlib/array-from-iterator
Description: Create (or fill) an array from an iterator.
Author: The Stdlib Authors
Latest version: 0.2.3

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# iterator2array

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> Create (or fill) an array 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/array-from-iterator
```

</section>

<section class="usage">

## Usage

```javascript
var iterator2array = require( '@stdlib/array-from-iterator' );
```

#### iterator2array( iterator\[, out]\[, mapFcn\[, thisArg]] )

Creates (or fills) an array from an `iterator`.

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

var opts = {
    'iter': 10
};

var arr = iterator2array( randu( opts ) );
// returns <Array>
```

By default, the function creates and fills a generic `array`. To fill an array-like `object`, provide an `out` argument.

```javascript
var Float64Array = require( '@stdlib/array-float64' );
var randu = require( '@stdlib/random-iter-randu' );

var out = new Float64Array( 10 );

var arr = iterator2array( randu(), out );
// returns <Float64Array>

var bool = ( out === arr );
// returns true
```

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

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

function fcn( v ) {
    return v * 10.0;
}

var arr = iterator2array( array2iterator( [ 1, 2, 3, 4 ] ), fcn );
// returns [ 10.0, 20.0, 30.0, 40.0 ]
```

The invoked function is provided two arguments:

-   **value**: iterated value.
-   **index**: iterated value index.

```javascript
var Float64Array = require( '@stdlib/array-float64' );
var randu = require( '@stdlib/random-iter-randu' );

function fcn( v, i ) {
    return v * (i+1);
}

var arr = iterator2array( randu(), new Float64Array( 10 ), fcn );
// returns <Float64Array>
```

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 = iterator2array( 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

-   If provided an output array, the function fills the output array with iterated values.
-   Iteration stops when an output array is full **or** an iterator finishes; whichever comes first.
-   By providing an output typed array, one avoids the temporary memory allocation when using the built-in `TypedArray.from`.

</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 iterator2array = require( '@stdlib/array-from-iterator' );

var opts;
var arr;
var it;
var i;

function scale( v, i ) {
    return v * (i+1);
}

// Create an iterator for generating uniformly distributed pseudorandom numbers:
opts = {
    'iter': 10
};
it = randu( opts );

// Fill an array with scaled iterator values:
arr = iterator2array( it, new Float64Array( opts.iter ), scale );

for ( i = 0; i < arr.length; i++ ) {
    console.log( arr[ i ] );
}
```

</section>

<!-- /.examples -->

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<section class="references">

</section>

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<section class="related">

* * *

## See Also

-   <span class="package-name">[`@stdlib/array-to-iterator`][@stdlib/array/to-iterator]</span><span class="delimiter">: </span><span class="description">create an iterator from an array-like object.</span>
-   <span class="package-name">[`@stdlib/iter-to-array-view`][@stdlib/iter/to-array-view]</span><span class="delimiter">: </span><span class="description">fill an array-like object view 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-license]: https://raw.githubusercontent.com/stdlib-js/array-from-iterator/main/LICENSE

<!-- <related-links> -->

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

[@stdlib/iter/to-array-view]: https://www.npmjs.com/package/@stdlib/iter-to-array-view

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</section>

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