@stdlib/iter/advance/README.md

Standard iterator utilities.

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# iterAdvance

> Advance an [iterator][mdn-iterator-protocol].

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## Usage

```javascript
var iterAdvance = require( '@stdlib/iter/advance' );
```

#### iterAdvance( iterator\[, n] )

Eagerly advances and returns a provided [`iterator`][mdn-iterator-protocol].

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

var arr = array2iterator( [ 0, 0, 0, 0, 1 ] );
var it = iterAdvance( arr );

var bool = ( it === arr );
// returns true

var v = it.next().done;
// returns true
```

By default, the function **eagerly** consumes an entire [`iterator`][mdn-iterator-protocol] (i.e., `n == 1e308`). To limit the number of iterations, provide a second argument.

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

var arr = array2iterator( [ 0, 0, 0, 0, 1 ] );
var it = iterAdvance( arr, 4 );

var bool = ( it === arr );
// returns true

var v = it.next().value;
// returns 1

bool = it.next().done;
// returns true
```

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## Notes

-   The function **eagerly** advances an input [iterator][mdn-iterator-protocol] `n` iterations or until the input [`iterator`][mdn-iterator-protocol] finishes, whichever comes first.

-   This function is equivalent to performing manual iteration using a `while` loop.

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

    var arr = array2iterator( [ 0, 0, 0, 0, 1 ] );

    var i = 0;
    var v;
    while ( i < 4 ) {
        v = arr.next();
        if ( v.done ) {
            break;
        }
        i += 1;
    }

    v = arr.next().value;
    // returns 1

    var bool = arr.next().done;
    // returns true
    ```

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## Examples

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

```javascript
var randu = require( '@stdlib/random/iter/randu' );
var iterLength = require( '@stdlib/iter/length' );
var iterAdvance = require( '@stdlib/iter/advance' );

// Create an iterator which generates uniformly distributed pseudorandom numbers:
var opts = {
    'iter': 100
};
var it1 = randu( opts );

// Discard the first 10 values:
var it2 = iterAdvance( it1, 10 );

// Determine the iterator length:
var len = iterLength( it2 );
// returns 90
```

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* * *

## See Also

-   <span class="package-name">[`@stdlib/iter/head`][@stdlib/iter/head]</span><span class="delimiter">: </span><span class="description">create an iterator which returns the first `n` values of a provided iterator.</span>
-   <span class="package-name">[`@stdlib/iter/slice`][@stdlib/iter/slice]</span><span class="delimiter">: </span><span class="description">create an iterator which returns a subsequence of iterated values from a provided iterator.</span>

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[mdn-iterator-protocol]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols#The_iterator_protocol

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[@stdlib/iter/head]: https://github.com/stdlib-js/iter/tree/main/head

[@stdlib/iter/slice]: https://github.com/stdlib-js/iter/tree/main/slice

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