npm package: @stdlib/utils-function-name
Description: Determine a function's name.
Author: The Stdlib Authors
Latest version: 0.2.3

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

# Function Name

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

> Determine a function's name.

<section class="installation">

## Installation

```bash
npm install @stdlib/utils-function-name
```

</section>

<section class="usage">

## Usage

```javascript
var functionName = require( '@stdlib/utils-function-name' );
```

#### functionName( fcn )

Returns the name of a `function`.

<!-- eslint-disable stdlib/no-builtin-math -->

```javascript
var v = functionName( Math.sqrt );
// returns 'sqrt'
```

If provided an **anonymous** `function`, the function returns an empty `string` or the string `"anonymous"`.

<!-- eslint-disable no-empty-function, func-names, no-restricted-syntax -->

```javascript
var v = functionName( function () {} );
// returns '' || 'anonymous'
```

If provided a value which is not a `function`, the function **throws** a `TypeError`.

```javascript
try {
    functionName( 'beep' );
    // throws error...
} catch ( err ) {
    console.error( err );
}
```

</section>

<!-- /.usage -->

<section class="notes">

## Notes

-   For more information regarding the naming of anonymous functions, see

    -   [Function Names in ES6][2ality-function-names]
    -   Webkit bug [7726][webkit-bug-7726]
    -   [MDN][mdn-function-name]

</section>

<!-- /.notes -->

<section class="examples">

## Examples

<!-- eslint-disable no-empty-function, no-restricted-syntax, func-names, stdlib/no-builtin-math -->

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

```javascript
var Float64Array = require( '@stdlib/array-float64' );
var Buffer = require( '@stdlib/buffer-ctor' );
var Number = require( '@stdlib/number-ctor' );
var Boolean = require( '@stdlib/boolean-ctor' );
var Function = require( '@stdlib/function-ctor' );
var functionName = require( '@stdlib/utils-function-name' );

var v = functionName( Math.sqrt );
// returns 'sqrt'

v = functionName( Float64Array );
// returns 'Float64Array'

v = functionName( Buffer );
// returns 'Buffer'

v = functionName( Date );
// returns 'Date'

v = functionName( String );
// returns 'String'

v = functionName( Boolean );
// returns 'Boolean'

v = functionName( Function );
// returns 'Function'

v = functionName( Number );
// returns 'Number'

v = functionName( function foo() {} );
// returns 'foo'

v = functionName( function () {} );
// returns '' || 'anonymous'
```

</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/utils-constructor-name`][@stdlib/utils/constructor-name]</span><span class="delimiter">: </span><span class="description">determine the name of a value's constructor.</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/utils-function-name.svg
[npm-url]: https://npmjs.org/package/@stdlib/utils-function-name

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

[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/utils-function-name/main.svg
[coverage-url]: https://codecov.io/github/stdlib-js/utils-function-name?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/utils-function-name/tree/deno
[deno-readme]: https://github.com/stdlib-js/utils-function-name/blob/deno/README.md
[umd-url]: https://github.com/stdlib-js/utils-function-name/tree/umd
[umd-readme]: https://github.com/stdlib-js/utils-function-name/blob/umd/README.md
[esm-url]: https://github.com/stdlib-js/utils-function-name/tree/esm
[esm-readme]: https://github.com/stdlib-js/utils-function-name/blob/esm/README.md
[branches-url]: https://github.com/stdlib-js/utils-function-name/blob/main/branches.md

[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/utils-function-name/main/LICENSE

[2ality-function-names]: http://www.2ality.com/2015/09/function-names-es6.html

[webkit-bug-7726]: https://bugs.webkit.org/show_bug.cgi?id=7726

[mdn-function-name]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/name

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

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

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

</section>

<!-- /.links -->