npm package: @stdlib/regexp-extname
Description: Return a regular expression to capture a filename extension.
Author: The Stdlib Authors
Latest version: 0.2.3

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<details>
  <summary>
    About stdlib...
  </summary>
  <p>We believe in a future in which the web is a preferred environment for numerical computation. To help realize this future, we've built stdlib. stdlib is a standard library, with an emphasis on numerical and scientific computation, written in JavaScript (and C) for execution in browsers and in Node.js.</p>
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</details>

# reExtname

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

> [Regular expression][regexp] to capture a filename extension.

<section class="installation">

## Installation

```bash
npm install @stdlib/regexp-extname
```

</section>

<section class="usage">

## Usage

```javascript
var reExtname = require( '@stdlib/regexp-extname' );
```

#### reExtname( \[platform] )

Returns a [regular expression][regexp] to capture a filename extension.

```javascript
var RE = reExtname();
// returns <RegExp>

RE = reExtname( 'posix' );
// returns <RegExp>

var ext = RE.exec( '/foo/bar/index.js' )[ 1 ];
// returns '.js'

RE = reExtname( 'win32' );
// returns <RegExp>

ext = RE.exec( 'C:\\foo\\bar\\index.js' )[ 1 ];
// returns '.js'
```

#### reExtname.REGEXP

[Regular expression][regexp] to capture a filename extension.

```javascript
var bool = ( reExtname.REGEXP.toString() === reExtname().toString() );
// returns true
```

#### reExtname.REGEXP_POSIX

[Regular expression][@stdlib/regexp/extname-posix] to capture a [POSIX][posix] filename extension.

```javascript
var ext = reExtname.REGEXP_POSIX.exec( '/foo/bar/index.js' )[ 1 ];
// returns '.js'
```

#### reExtname.REGEXP_WIN32

[Regular expression][@stdlib/regexp/extname-windows] to capture a Windows filename extension.

```javascript
var ext = reExtname.REGEXP_WIN32.exec( 'C:\\foo\\bar\\index.js' )[ 1 ];
// returns '.js'
```

</section>

<!-- /.usage -->

<section class="notes">

## Notes

-   The as `REGEXP` exported [regular expression][regexp] is [platform][@stdlib/assert/is-windows]-dependent. If the current process is running on Windows, `REGEXP === REGEXP_WIN32`; otherwise, `REGEXP === REGEXP_POSIX`.

</section>

<!-- /.notes -->

<section class="examples">

## Examples

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

```javascript
var reExtname = require( '@stdlib/regexp-extname' );
var RE_EXTNAME = reExtname();
var ext;

// Assuming a POSIX platform...
ext = RE_EXTNAME.exec( '/foo/bar/index.js' )[ 1 ];
// returns '.js'

ext = reExtname.REGEXP_WIN32.exec( '/foo/bar/home.html' )[ 1 ];
// returns '.html'

ext = reExtname.REGEXP_WIN32.exec( 'C:\\foo\\bar\\home.html' )[ 1 ];
// returns '.html'
```

</section>

<!-- /.examples -->

<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->

<section class="related">

* * *

## See Also

-   <span class="package-name">[`@stdlib/regexp-extname-posix`][@stdlib/regexp/extname-posix]</span><span class="delimiter">: </span><span class="description">return a regular expression to capture a POSIX filename extension.</span>
-   <span class="package-name">[`@stdlib/regexp-extname-windows`][@stdlib/regexp/extname-windows]</span><span class="delimiter">: </span><span class="description">return a regular expression to capture a Windows filename extension.</span>
-   <span class="package-name">[`@stdlib/utils-extname`][@stdlib/utils/extname]</span><span class="delimiter">: </span><span class="description">return a filename extension.</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/regexp-extname.svg
[npm-url]: https://npmjs.org/package/@stdlib/regexp-extname

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

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

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[stdlib]: https://github.com/stdlib-js/stdlib

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

[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/regexp-extname/main/LICENSE

[regexp]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions

[posix]: https://en.wikipedia.org/wiki/POSIX

[@stdlib/assert/is-windows]: https://www.npmjs.com/package/@stdlib/assert-is-windows

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

[@stdlib/regexp/extname-posix]: https://www.npmjs.com/package/@stdlib/regexp-extname-posix

[@stdlib/regexp/extname-windows]: https://www.npmjs.com/package/@stdlib/regexp-extname-windows

[@stdlib/utils/extname]: https://www.npmjs.com/package/@stdlib/utils-extname

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

</section>

<!-- /.links -->