Rollup tool to bundle ES6 modules into trim CJS files

rollup, prepublish
npm install rollup-prepublish@1.3.0



A Rollup-based CLI with some handy defaults, useful as a prepublish script for library authors.

What it does:

The goal is to take your first-party and third-party ES6 modules and bundle them into a very trim CommonJS file, suitable to be exported to CommonJS users.


npm install -g rollup-prepublish


rollup-prepublish index.js > bundle.js
rollup-prepublish --browser index.js > bundle-browser.js

In --browser mode, Rollup will use the "browser" field if it's available to serve up the "browser" version of the module. You may need to do this if any of your dependencies are using "browser".

You can pass in the input file and output file as the first and second arguments, or else it will assume CWD for the first (locating the main index.js as necessary) and stdout for the second.

Example prepublish script:

// package.json
  /* ... */
  "scripts": {
    "prepublish": "rollup-prepublish > lib/index.js && rollup-prepublish --browser > lib/browser.js"
  "main": {
  "browser": {
    "lib/index.js": "lib/browser.js"
  /* ... */

With the above configuration, CommonJS consumers will get:

  • lib/index.js if they are using Node, and
  • lib/browser.js if they are using Webpack, Browserify, etc.

Also, Rollup consumers will get src/index.js (assuming that's your ES6 source).

--help output

Usage: rollup-prepublish [options] [inputFile] [outputFile]

  -b, --browser           Bundle using browser-resolve instead of node-resolve
  -f, --fix-dependencies  Update dependencies in package.json to add external
                          deps                                         [boolean]
  -q, --quiet             Don't print warnings about excluded/included deps
  -h, --help              Show help                                    [boolean]

  rollup-prepublish            Bundle current project and output to stdout
  rollup-prepublish --browser  Same thing, but emit a browser bundle
  rollup-prepublish --quiet    Silence warnings


Since third-party ES6 modules are bundled by default, you can include them in your devDependencies instead of regular dependencies. (No reason to ship them to consumers, which unnecessarily increases npm install time!) On the other hand, note that this will prevent de-duplication of shared modules.

If you do so, though, then any transitive dependencies should now be treated as regular dependencies. You can automatically add them to your package.json using --fix-dependencies.

Also, if you have any "browser" code in your ES6 source, you should add those to "browser" as well:

  "browser": {
    "lib/index.js": "lib/browser.js",
    "src/somefile.js": "src/somefile-browser.js"

You may also want to add a "jsnext:main" or "module" to your own package.json, so that consumers of your library can use rollup-prepublish script and get the same benefits.

  "module": {

JavaScript API

There's also a straight-up JavaScript API:

var rollupPrepublish = require('rollup-prepublish');
  entry: 'index.js',
  dest: 'bundle.js',
  browser: true, // false by default
  fixDependencies: true, // false by default
  quiet: true // false by default
}).then(function (code) {
  // if you don't specify a `dest`, then the code will be returned here
  // as a string
  console.log('code: ', code)
}).catch(function (err) {