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1# Rollup
2
3<p align="center">
4 <a href="https://www.npmjs.com/package/rollup">
5 <img src="https://img.shields.io/npm/v/rollup.svg" alt="npm version" >
6 </a>
7 <a href="https://packagephobia.now.sh/result?p=rollup">
8 <img src="https://packagephobia.now.sh/badge?p=rollup" alt="install size" >
9 </a>
10 <a href="https://codecov.io/gh/rollup/rollup">
11 <img src="https://codecov.io/gh/rollup/rollup/graph/badge.svg" alt="code coverage" >
12 </a>
13 <a href="#backers" alt="sponsors on Open Collective">
14 <img src="https://opencollective.com/rollup/backers/badge.svg" alt="backers" >
15 </a>
16 <a href="#sponsors" alt="Sponsors on Open Collective">
17 <img src="https://opencollective.com/rollup/sponsors/badge.svg" alt="sponsors" >
18 </a>
19 <a href="https://github.com/rollup/rollup/blob/master/LICENSE.md">
20 <img src="https://img.shields.io/npm/l/rollup.svg" alt="license">
21 </a>
22 <a href="https://david-dm.org/rollup/rollup">
23 <img src="https://david-dm.org/rollup/rollup/status.svg" alt="dependency status">
24 </a>
25 <a href='https://is.gd/rollup_chat?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge'>
26 <img src='https://img.shields.io/discord/466787075518365708?color=778cd1&label=chat' alt='Join the chat at https://is.gd/rollup_chat'>
27 </a>
28</p>
29
30
31## Overview
32
33Rollup is a module bundler for JavaScript which compiles small pieces of code into something larger and more complex, such as a library or application. It uses the standardized ES module format for code, instead of previous idiosyncratic solutions such as CommonJS and AMD. ES modules let you freely and seamlessly combine the most useful individual functions from your favorite libraries. Rollup can optimize ES modules for faster native loading in modern browsers, or output a legacy module format allowing ES module workflows today.
34
35## Quick Start Guide
36
37Install with `npm install --global rollup`. Rollup can be used either through a [command line interface](https://rollupjs.org/#command-line-reference) with an optional configuration file, or else through its [JavaScript API](https://rollupjs.org/guide/en/#javascript-api). Run `rollup --help` to see the available options and parameters. The starter project templates, [rollup-starter-lib](https://github.com/rollup/rollup-starter-lib) and [rollup-starter-app](https://github.com/rollup/rollup-starter-app), demonstrate common configuration options, and more detailed instructions are available throughout the [user guide](https://rollupjs.org/).
38
39### Commands
40
41These commands assume the entry point to your application is named main.js, and that you'd like all imports compiled into a single file named bundle.js.
42
43For browsers:
44
45```bash
46# compile to a <script> containing a self-executing function
47rollup main.js --format iife --name "myBundle" --file bundle.js
48```
49
50For Node.js:
51
52```bash
53# compile to a CommonJS module
54rollup main.js --format cjs --file bundle.js
55```
56
57For both browsers and Node.js:
58
59```bash
60# UMD format requires a bundle name
61rollup main.js --format umd --name "myBundle" --file bundle.js
62```
63
64## Why
65
66Developing software is usually easier if you break your project into smaller separate pieces, since that often removes unexpected interactions and dramatically reduces the complexity of the problems you'll need to solve, and simply writing smaller projects in the first place [isn't necessarily the answer](https://medium.com/@Rich_Harris/small-modules-it-s-not-quite-that-simple-3ca532d65de4). Unfortunately, JavaScript has not historically included this capability as a core feature in the language.
67
68This finally changed with ES modules support in JavaScript, which provides a syntax for importing and exporting functions and data so they can be shared between separate scripts. The specification is now implemented in all major browsers and in Node.js behind the --experimental-modules flag for ".mjs" files. Rollup allows you to write your code using this module system, either outputting optimized ES modules for use in these native environments, or compiling it back down to existing supported formats such as CommonJS modules, AMD modules, and IIFE-style scripts. This means that you get to *write future-proof code*, and you also get the tremendous benefits of...
69
70## Tree Shaking
71
72In addition to enabling the use of ES modules, Rollup also statically analyzes and optimizes the code you are importing, and will exclude anything that isn't actually used. This allows you to build on top of existing tools and modules without adding extra dependencies or bloating the size of your project.
73
74For example, with CommonJS, the *entire tool or library must be imported*.
75
76```js
77// import the entire utils object with CommonJS
78var utils = require( 'utils' );
79var query = 'Rollup';
80// use the ajax method of the utils object
81utils.ajax( 'https://api.example.com?search=' + query ).then( handleResponse );
82```
83
84But with ES modules, instead of importing the whole `utils` object, we can just import the one `ajax` function we need:
85
86```js
87// import the ajax function with an ES import statement
88import { ajax } from 'utils';
89var query = 'Rollup';
90// call the ajax function
91ajax( 'https://api.example.com?search=' + query ).then( handleResponse );
92```
93
94Because Rollup includes the bare minimum, it results in lighter, faster, and less complicated libraries and applications. Since this approach is based on explicit `import` and `export` statements, it is vastly more effective than simply running an automated minifier to detect unused variables in the compiled output code.
95
96## Compatibility
97
98### Importing CommonJS
99
100Rollup can import existing CommonJS modules [through a plugin](https://github.com/rollup/plugins/tree/master/packages/commonjs).
101
102### Publishing ES Modules
103
104To make sure your ES modules are immediately usable by tools that work with CommonJS such as Node.js and webpack, you can use Rollup to compile to UMD or CommonJS format, and then point to that compiled version with the `main` property in your `package.json` file. If your `package.json` file also has a `module` field, ES-module-aware tools like Rollup and [webpack 2](https://webpack.js.org/) will [import the ES module version](https://github.com/rollup/rollup/wiki/pkg.module) directly.
105
106## Contributors
107
108This project exists thanks to all the people who contribute. [[Contribute](CONTRIBUTING.md)].
109<a href="https://github.com/rollup/rollup/graphs/contributors"><img src="https://opencollective.com/rollup/contributors.svg?width=890" /></a>
110
111
112## Backers
113
114Thank you to all our backers! 🙏 [[Become a backer](https://opencollective.com/rollup#backer)]
115
116<a href="https://opencollective.com/rollup#backers" target="_blank"><img src="https://opencollective.com/rollup/backers.svg?width=890"></a>
117
118
119## Sponsors
120
121Support this project by becoming a sponsor. Your logo will show up here with a link to your website. [[Become a sponsor](https://opencollective.com/rollup#sponsor)]
122
123<a href="https://opencollective.com/rollup/sponsor/0/website" target="_blank"><img src="https://opencollective.com/rollup/sponsor/0/avatar.svg"></a>
124<a href="https://opencollective.com/rollup/sponsor/1/website" target="_blank"><img src="https://opencollective.com/rollup/sponsor/1/avatar.svg"></a>
125<a href="https://opencollective.com/rollup/sponsor/2/website" target="_blank"><img src="https://opencollective.com/rollup/sponsor/2/avatar.svg"></a>
126<a href="https://opencollective.com/rollup/sponsor/3/website" target="_blank"><img src="https://opencollective.com/rollup/sponsor/3/avatar.svg"></a>
127<a href="https://opencollective.com/rollup/sponsor/4/website" target="_blank"><img src="https://opencollective.com/rollup/sponsor/4/avatar.svg"></a>
128<a href="https://opencollective.com/rollup/sponsor/5/website" target="_blank"><img src="https://opencollective.com/rollup/sponsor/5/avatar.svg"></a>
129<a href="https://opencollective.com/rollup/sponsor/6/website" target="_blank"><img src="https://opencollective.com/rollup/sponsor/6/avatar.svg"></a>
130<a href="https://opencollective.com/rollup/sponsor/7/website" target="_blank"><img src="https://opencollective.com/rollup/sponsor/7/avatar.svg"></a>
131<a href="https://opencollective.com/rollup/sponsor/8/website" target="_blank"><img src="https://opencollective.com/rollup/sponsor/8/avatar.svg"></a>
132<a href="https://opencollective.com/rollup/sponsor/9/website" target="_blank"><img src="https://opencollective.com/rollup/sponsor/9/avatar.svg"></a>
133
134
135
136## License
137
138[MIT](https://github.com/rollup/rollup/blob/master/LICENSE.md)