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# iterator2array

> Create (or fill) an array from an iterator.

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## 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>

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## 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`.

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## 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>

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</section>

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* * *

## 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>

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

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

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</section>

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