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A boilerplate to author libraries in ES2015 for Node and the browser.


  • Author in ES2015 (even the unit tests)
  • Export as ES5 & UMD
  • Mocha-Chai-Sinon testing stack
  • Unit tests that work in Node and in the browser

Getting Started

Update the the name in the LICENSE and the information in package.json.

Write your code in src. The primary file is index.js (although the filename can be changed).

Run gulp build to compile the source into a distributable format.

Put your unit tests in test/unit. The gulp command runs the tests.

Gulp tasks

  • gulp - Lint the library and tests, then run the unit tests
  • gulp build - Lint then build the library
  • gulp watch - Continuously run the unit tests as you make changes to the source and test files themselves
  • gulp test-browser - Build the library for use with the browser spec runner. Changes to the source will cause the runner to automatically refresh.

Browser Tests

The browser spec runner can be opened in a browser to run your tests. For it to work, you must first run gulp test-browser. This will set up a watch task that will automatically refresh the tests when your scripts, or the tests, change.

Code Climate

This library is set up to integrate with Code Climate. If you've never used Code Climate, then you might be wondering why it's useful. There are two reasons:

  1. It consumes code coverage reports, and provides a coverage badge for the README
  2. It provides interesting stats on your library, if you're into that kinda thing

Either of these items on the list can simply be ignored if you're uninterested in them. Or you can pull Code Climate out entirely from the boilerplate and not worry about it. To do that, update the relevant Gulp tasks and the Travis build.

If you'd like to set up Code Climate for your project, follow the steps here.


This boilerplate uses ESLint and JSCS to lint your source. To change the rules, edit the .eslintrc and .jscsrc files in the root directory, respectively.

Given that your unit tests aren't your library code, it makes sense to lint them against a separate ESLint configuration. For this reason, a separate, unit-test specific .eslintrc can be found in the test directory. Unlike ESLint, the same JSCS rules are applied to both your code and your tests.


When should I consider using this boilerplate?

You're authoring any library that exports a single file. Examples are small libraries, or even entire JavaScript web applications. I use this boilerplate for both!

When might I not want to use this boilerplate?

You can always use this boilerplate as inspiration, but it works best for smaller libraries. If you're building a full-scale webapp, you will likely need many more changes to the build system.

What's the browser compatibility?

As a rule of thumb, this transpiler works best in IE9+. You can support IE8 by limiting yourself to a subset of ES2015 features. The Babel caveats page does an excellent job at explaining the nitty gritty details of supporting legacy browsers.

Are there examples?

Quite a few! Check them out on the wiki.

Is there a Yeoman generator?

There sure is.

Is there a version for Node-only projects?

Yup. It has fewer pieces on account of no longer running the tests in the browser. Check it out over here.


This boilerplate is, to a certain extent, easily customizable. To make changes, find what you're looking to do below and follow the instructions.

I want to change the primary source file

The primary source file for the library is src/index.js. Only the files that this file imports will be included in the final build. To change the name of this entry file:

  1. Rename the file
  2. Update the value of entryFileName in package.json under babelBoilerplateOptions

I want to change the exported file name

  1. Update main in package.json

I want to change the destination directory

  1. Update main in package.json

I want to change what variable my module exports

MyLibrary is the name of the variable exported from this boilerplate. You can change this by following these steps:

  1. Ensure that the variable you're exporting exists in your scripts
  2. Update the value of exportVarName in package.json under babelBoilerplateOptions
  3. Check that the unit tests have been updated to reference the new value

I don't want to export a variable

  1. Ensure that your entry file does not export anything
  2. Set the property of exportVarName in package.json to be "null"

My library depends on an external module

In the simplest case, you just need to install the module and use it in your scripts.

If you want to access the module itself in your unit test files, you will need to set up the test environment to support the module. To do this:

  1. Load the module in the test setup file. Attach any exported variables to global object if you'll be using them in your tests.
  2. Add those same global variables to the mochaGlobals array in package.json under babelBoilerplateOptions

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npm i babel-library-boilerplate

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