npm package: @stdlib/function-to-string
Description: Return a string representing the source code of a provided function.
Author: The Stdlib Authors
Latest version: 0.2.3

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# function2string

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

> Return a string representing the source code of a provided function.

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<section class="intro">

</section>

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<!-- Package usage documentation. -->

<section class="installation">

## Installation

```bash
npm install @stdlib/function-to-string
```

</section>

<section class="usage">

## Usage

```javascript
var function2string = require( '@stdlib/function-to-string' );
```

#### function2string( fcn )

Returns a string representing the source code of a provided function.

```javascript
function add( x, y ) {
    return x + y;
}

var str = function2string( add );
// e.g., returns 'function add( x, y ) {\n    return x + y;\n}'
```

</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

-   If called on built-in functions, functions created by `Function.prototype.bind()`, or other non-JavaScript functions, the function returns a "native" function string similar to the following:

    ```text
    "function foo() { [native code] }"
    ```

    For intrinsic object methods and functions, `foo` is the initial name of the function.

-   If called on a function created by the [`Function`][@stdlib/function/ctor] constructor, the function returns the source code of a synthesized function declaration having the name "anonymous" and using the provided parameters and function body.

-   Starting in ES2018, the ECMAScript specification requires that the returned string contain the exact same source code as it was declared, including any whitespace and/or comments. If the host is unable to access the source code, the specification requires that the returned string be the native function string.

</section>

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<!-- Package usage examples. -->

<section class="examples">

## Examples

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

```javascript
var ndarray = require( '@stdlib/ndarray-ctor' );
var erf = require( '@stdlib/math-base-special-erf' );
var daxpy = require( '@stdlib/blas-base-daxpy' );
var kebabcase = require( '@stdlib/string-kebabcase' );
var randu = require( '@stdlib/random-base-randu' );
var format = require( '@stdlib/string-format' );
var function2string = require( '@stdlib/function-to-string' );

var fcns = [
    [ 'ndarray', ndarray ],
    [ 'erf', erf ],
    [ 'daxpy', daxpy ],
    [ 'kebabcase', kebabcase ],
    [ 'randu', randu ],
    [ 'format', format ],
    [ 'function2string', function2string ]
];

var i;
for ( i = 0; i < fcns.length; i++ ) {
    console.log( format( 'Function: %s\n\n%s\n', fcns[ i ][ 0 ], function2string( fcns[ i ][ 1 ] ) ) );
}
```

</section>

<!-- /.examples -->

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</section>

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* * *

## See Also

-   <span class="package-name">[`@stdlib/function-ctor`][@stdlib/function/ctor]</span><span class="delimiter">: </span><span class="description">function constructor.</span>

</section>

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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/function-to-string

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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/function-to-string/tree/deno
[deno-readme]: https://github.com/stdlib-js/function-to-string/blob/deno/README.md
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[branches-url]: https://github.com/stdlib-js/function-to-string/blob/main/branches.md

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

[@stdlib/function/ctor]: https://www.npmjs.com/package/@stdlib/function-ctor

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