npm package: @stdlib/iter-dedupe
Description: Create an iterator which removes consecutive duplicated values.
Author: The Stdlib Authors
Latest version: 0.2.3

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    About stdlib...
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# iterDedupe

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

> Create an [iterator][mdn-iterator-protocol] which removes consecutive duplicated values.

<!-- 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-dedupe
```

</section>

<section class="usage">

## Usage

```javascript
var iterDedupe = require( '@stdlib/iter-dedupe' );
```

#### iterDedupe( iterator\[, limit] )

Returns an [iterator][mdn-iterator-protocol] which removes consecutive duplicated values.

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

var it = iterDedupe( array2iterator( [ 1, 1, 2, 3, 3, 3, 4, 4 ] ) );
// returns <Object>

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

v = it.next().value;
// returns 2

v = it.next().value;
// returns 3

v = it.next().value;
// returns 4

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

The returned [iterator][mdn-iterator-protocol] protocol-compliant object has the following properties:

-   **next**: function which returns an [iterator][mdn-iterator-protocol] protocol-compliant object containing the next iterated value (if one exists) assigned to a `value` property and a `done` property having a `boolean` value indicating whether the [iterator][mdn-iterator-protocol] is finished.
-   **return**: function which closes an [iterator][mdn-iterator-protocol] and returns a single (optional) argument in an [iterator][mdn-iterator-protocol] protocol-compliant object.

The returned [iterator][mdn-iterator-protocol] removes **consecutive** duplicated values and does **not** return globally unique values.

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

var it = iterDedupe( array2iterator( [ 1, 1, 2, 1, 1, 2 ] ) );
// returns <Object>

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

v = it.next().value;
// returns 2

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

v = it.next().value;
// returns 2

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

To specify the number of allowed consecutive duplicated values, provide a second argument.

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

var it = iterDedupe( array2iterator( [ 1, 1, 2, 3, 3, 3, 3, 4, 4, 4 ] ), 2 );
// returns <Object>

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

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

v = it.next().value;
// returns 2

v = it.next().value;
// returns 3

v = it.next().value;
// returns 3

v = it.next().value;
// returns 4

v = it.next().value;
// returns 4

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

</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

-   `NaN` values are considered **distinct**.

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

    var it = iterDedupe( array2iterator( [ NaN, NaN, NaN, NaN ] ) );
    // returns <Object>

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

    v = it.next().value;
    // returns NaN

    v = it.next().value;
    // returns NaN

    v = it.next().value;
    // returns NaN

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

-   Uniqueness is determined according to strict equality. Accordingly, objects are **not** checked for deep equality.

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

    var it = iterDedupe( array2iterator( [ {}, {}, {}, {} ] ) );
    // returns <Object>

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

    v = it.next().value;
    // returns {}

    v = it.next().value;
    // returns {}

    v = it.next().value;
    // returns {}

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

-   If an environment supports `Symbol.iterator` **and** a provided [iterator][mdn-iterator-protocol] is iterable, the returned [iterator][mdn-iterator-protocol] is iterable.

</section>

<!-- /.notes -->

<!-- Package usage examples. -->

<section class="examples">

## Examples

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

```javascript
var randi = require( '@stdlib/random-iter-discrete-uniform' );
var iterDedupe = require( '@stdlib/iter-dedupe' );

// Create a seeded iterator for generating pseudorandom integers on the interval [1,3]:
var rand = randi( 1, 3, {
    'seed': 1234,
    'iter': 100
});

// Create an iterator which limits "runs" to at most 3 values:
var it = iterDedupe( rand, 3 );

// Perform manual iteration...
var v;
while ( true ) {
    v = it.next();
    if ( v.done ) {
        break;
    }
    console.log( v.value );
}
```

</section>

<!-- /.examples -->

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<section class="references">

</section>

<!-- /.references -->

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<section class="related">

* * *

## See Also

-   <span class="package-name">[`@stdlib/iter-dedupe-by`][@stdlib/iter/dedupe-by]</span><span class="delimiter">: </span><span class="description">create an iterator which removes consecutive values that resolve to the same value according to a provided function.</span>
-   <span class="package-name">[`@stdlib/iter-unique`][@stdlib/iter/unique]</span><span class="delimiter">: </span><span class="description">create an iterator which returns unique values.</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

[![Chat][chat-image]][chat-url]

---

## License

See [LICENSE][stdlib-license].


## Copyright

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

</section>

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[npm-url]: https://npmjs.org/package/@stdlib/iter-dedupe

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[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-dedupe/tree/deno
[deno-readme]: https://github.com/stdlib-js/iter-dedupe/blob/deno/README.md
[umd-url]: https://github.com/stdlib-js/iter-dedupe/tree/umd
[umd-readme]: https://github.com/stdlib-js/iter-dedupe/blob/umd/README.md
[esm-url]: https://github.com/stdlib-js/iter-dedupe/tree/esm
[esm-readme]: https://github.com/stdlib-js/iter-dedupe/blob/esm/README.md
[branches-url]: https://github.com/stdlib-js/iter-dedupe/blob/main/branches.md

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

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

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

[@stdlib/iter/dedupe-by]: https://www.npmjs.com/package/@stdlib/iter-dedupe-by

[@stdlib/iter/unique]: https://www.npmjs.com/package/@stdlib/iter-unique

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</section>

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