rollup-starter-project

This package shows how to get started with rollup (and babel) for writing npm packages using ES6 modules. Writing npm packages with a jsnext:main allows users of your package to choose whether they use it using the traditional require function understood by node.js, or using the import statement added in ES6 which can result in smaller bundles through live-code inclusion static analysis.

Usage

You can simply use this project as inspiration for how to configure your own, or clone it and edit the metadata files when starting your own project (i.e. README.md, package.json, and LICENSE).

lib/index.js

This is the main source file in your application, and the main file you'll start editing to implement the functionality of your package. As shown in this example, you can import other files from this file similarly to how you would require packages typically (e.g. lib/utils.js).

test/index_test.js

This is the starting point for tests in your package. You should import the code to test from lib/ as shown in the example. The project is already configured to use mocha when you run npm test.

dist/rollup-starter-project.js

This is the main file of the package and includes all the code needed to run your package. It is in UMD format, meaning it can be used in most JavaScript runtime environments. If your package has dependencies you do not want bundled, be sure to configure rollup to exclude them by marking them as external. By default all dependencies entries in your package.json will be external.

dist/rollup-starter-project.mjs

This is the jsnext:main file of the package and includes all the code needed to run your package. Compared to the UMD version, this one preserves ES6 imports and exports at the package boundary for tools that support it (such as rollup). If your package has dependencies you do not want bundled, be sure to configure rollup to exclude them by marking them as external. By default all dependencies entries in your package.json will be external.

.eslintrc

This controls how the package is linted and starts off with the recommended set of rules from eslint itself. It also uses babel-eslint to parse your code, allowing syntax that the standard eslint parser may not understand (e.g. type annotations).

Dependencies

This section explains what all the dependencies are and what they're for, so you can decide which ones you actually need.

babel-eslint

Enables eslint to understand all JavaScript syntax that babel understands, and adds a few rules for linting ES2015 code. This can be removed if you plan not to use babel to transform ES2015 code to ES5 or if you plan not to use eslint.

babel-plugin-external-helpers

Ensures that only one copy of each babel helper is included in the bundle when used with rollup. This can be removed if you plan not to use babel to transform ES2015 code to ES5.

babel-preset-es2015

Used when babel is used without rollup, and referenced by the .babelrc file. This can be removed if you plan not to use babel to transform ES2015 code to ES5 or you plan to specify all the babel plugins manually.

babel-register

Provides on-demand transpilation via babel so no precompilation is required. This is used in the tests to allow running them without compiling first, and is referenced in test/mocha.opts.

babelrc-rollup

Handles transforming the babel config from .babelrc to one suitable for use with rollup-plugin-babel, where you don't want to use any module plugins.

eslint

eslint checks your code for common errors and ensures it adheres to the style you configure in .eslintrc. You can remove this if you plan not to lint your code or if you're using another linter, such as jshint or jscs.

mocha

mocha is a test runner. You can remove this if you plan not to write tests (don't do that!) or if you plan to use another test runner such as Jasmine.

istanbul

istanbul is a code coverage tool that computes statement, line, function and branch coverage with module loader hooks to transparently add coverage when running tests. You can remove this dependency if you won't be writing tests or you don't care about code coverage.

You'll also have to change the test/mocha.opts file and remove the custom reporter option --reporter test/istanbul.reporter.js. After that you can safely delete the test/istanbul.reporter.js file.

rollup

rollup is a JavaScript module bundler and the reason you're looking at this project in the first place, so you probably don't want to remove this dependency.

rollup-plugin-babel

This plugin enables support for babel, which transforms ES2015 code to ES5. You can remove this if you plan not to use ES2015 code.

rollup-plugin-istanbul

This plugin provides seamless integration between Rollup and Istanbul to generate code coverage reports of your project. If you don't plan to write tests or simply don't care about code coverage, you can safely remove this along with Istanbul.

Just like with the Istanbul dependency, you should change the test/mocha.opts file. Read the above instructions for removing Istanbul.

Contributing

If you think a project built with rollup should be set up differently, open an issue to discuss it or create a pull request.