npm package: @stdlib/iter-unique
Description: Create an iterator which returns unique values.
Author: The Stdlib Authors
Latest version: 0.2.3

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<details>
  <summary>
    About stdlib...
  </summary>
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# iterUnique

[![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 returns unique 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>

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<!-- Package usage documentation. -->

<section class="installation">

## Installation

```bash
npm install @stdlib/iter-unique
```

</section>

<section class="usage">

## Usage

```javascript
var iterUnique = require( '@stdlib/iter-unique' );
```

#### iterUnique( iterator )

Returns an [iterator][mdn-iterator-protocol] which returns unique values.

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

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

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

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

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

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

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.

</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

-   Value "uniqueness" is determined according to **strict equality**.
-   A returned [iterator][mdn-iterator-protocol] internally buffers unique values and, thus, has `O(N)` memory requirements.
-   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 discreteUniform = require( '@stdlib/random-iter-discrete-uniform' );
var iterUnique = require( '@stdlib/iter-unique' );

// Create a seeded iterator which can generate 1000 pseudorandom numbers:
var rand = discreteUniform( 1, 10, {
    'seed': 1234,
    'iter': 1000
});

// Create an iterator which returns unique values:
var it = iterUnique( rand );

// 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>

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<section class="related">

* * *

## See Also

-   <span class="package-name">[`@stdlib/iter-unique-by`][@stdlib/iter/unique-by]</span><span class="delimiter">: </span><span class="description">create an iterator which returns unique values according to a predicate function.</span>
-   <span class="package-name">[`@stdlib/iter-unique-by-hash`][@stdlib/iter/unique-by-hash]</span><span class="delimiter">: </span><span class="description">create an iterator which returns unique values according to a hash function.</span>

</section>

<!-- /.related -->

<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->


<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>

<!-- /.stdlib -->

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<section class="links">

[npm-image]: http://img.shields.io/npm/v/@stdlib/iter-unique.svg
[npm-url]: https://npmjs.org/package/@stdlib/iter-unique

[test-image]: https://github.com/stdlib-js/iter-unique/actions/workflows/test.yml/badge.svg?branch=v0.2.3
[test-url]: https://github.com/stdlib-js/iter-unique/actions/workflows/test.yml?query=branch:v0.2.3

[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/iter-unique/main.svg
[coverage-url]: https://codecov.io/github/stdlib-js/iter-unique?branch=main

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

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

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

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

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

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

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</section>

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