npm package: @stdlib/utils-compose
Description: Function composition.
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>

# compose

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

> [Function composition][function-composition].

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<section class="intro">

</section>

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<!-- Package usage documentation. -->

<section class="installation">

## Installation

```bash
npm install @stdlib/utils-compose
```

</section>

<section class="usage">

## Usage

```javascript
var compose = require( '@stdlib/utils-compose' );
```

#### compose( ...fcn )

Returns a composite function. Starting from the right, the composite function evaluates each function and passes the result as an argument to the next function. The result of the leftmost function is the result of the whole.

```javascript
function a( x ) {
    return 2 * x;
}

function b( x ) {
    return x + 3;
}

function c( x ) {
    return x / 5;
}

var f = compose( c, b, a );

var z = f( 6 ); // ((2*x)+3)/5
// returns 3
```

**Only** the rightmost function is explicitly permitted to accept multiple arguments. All other functions are evaluated as **unary** functions.

```javascript
function a( x, y ) {
    return (x*5) + (y*3);
}

function b( r ) {
    return r + 12;
}

var f = compose( b, a );

var z = f( 4, 6 );
// returns 50
```

</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

-   The function will throw if provided fewer than `2` input arguments.

</section>

<!-- /.notes -->

<!-- Package usage examples. -->

<section class="examples">

## Examples

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

```javascript
var compose = require( '@stdlib/utils-compose' );

function a( x, y ) {
    return x * y;
}

function b( z ) {
    return z + 5;
}

function c( r ) {
    return r / 10;
}

var f = compose( c, b, a );

var v = f( 5, 3 );
// returns 2
```

</section>

<!-- /.examples -->

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<section class="related">

* * *

## See Also

-   <span class="package-name">[`@stdlib/utils-async/compose`][@stdlib/utils/async/compose]</span><span class="delimiter">: </span><span class="description">function composition.</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-image]: http://img.shields.io/npm/v/@stdlib/utils-compose.svg
[npm-url]: https://npmjs.org/package/@stdlib/utils-compose

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

[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/utils-compose/main.svg
[coverage-url]: https://codecov.io/github/stdlib-js/utils-compose?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/utils-compose/tree/deno
[deno-readme]: https://github.com/stdlib-js/utils-compose/blob/deno/README.md
[umd-url]: https://github.com/stdlib-js/utils-compose/tree/umd
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[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/utils-compose/main/LICENSE

[function-composition]: https://en.wikipedia.org/wiki/Function_composition_%28computer_science%29

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

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</section>

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