CONTRIBUTING.md

Contributing

Contributions are always welcome. If you don't know what how you can help, you can check issues or ask @zloirock.

How to add a new polyfill

• The polyfill implementation should be added to the packages/core-js/modules directory.
• If the implementation for the pure version should differ from the global version, it should be added to packages/core-js-pure/override directory. The rest of core-js-pure will be copied from core-js package.
• For export the polyfill, in almost all cases should be used _export helper.
• The polyfill should be added to the list of polyfills and to entry points, where it's required: packages/core-js/index.js, directories packages/core-js/features, packages/core-js/es, packages/core-js/esnext and packages/core-js/web.
• Unit tests for the polyfill should be added to tests/tests and tests/pure.
• All new entry points should be added to the test of entry points.
• Add it to README.md.

Style and standards

Coding style should follow our .eslintrc. You can test it by calling npm run eslint. Different places have different syntax and standard library limitations:

• Polyfill implementations should use only ES3 syntax and standard library. Polyfills should not use another polyfill from the global namespace.
• In unit tests should be used modern syntax with our minimalistic Babel config. Unit tests for the pure version should not use any modern standard library features.
• In building tools and tests, performed in Node.js, should be used only available in Node.js 4 syntax and standard library.

File names should be in kebab-case. Name of files with polyfills should follow naming convention namespace.subnamespase-where-required.feature-name, for example, esnext.promise.try. Top level namespace could be es for stable ECMAScript features, esnext for ECMAScript proposals, web for another web standards and core for helpers. Internal core-js modules should use _ prefix.

Testing

Before testing, you should install dependencies:

$ npm i

You can run all tests by

$ npm run test

You can run parts of the test case separately:

• Linting:

$ npm run lint

• Global version unit tests:

$ npm run unit-tests

• pure version unit tests:

$ npm run unit-tests-pure

• Promises/A+ test case:

$ npm run promises-tests

• ECMAScript Observable test case:

$ npm run observables-tests

• CommonJS entry points tests:

$ npm run commonjs-tests

If you want to run tests in a certain browser at first you should build packages and test bundles:

$ npm run build

• For running global version unit test case use this file:

tests/tests.html

• For running the pure version unit test case use this file:

tests/pure.html

• Before running Promises/A+ test case in the browser you should bundle it:

$ npm run bundle-promises-tests

and after that use this file:

tests/promises-aplus.html