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OOjs is a JavaScript library for working with objects.

Key features include inheritance, mixins and utilities for working with objects.

/* Example */
( function ( oo ) {
    function Animal() {}
    function Magic() {}
    function Unicorn() { this ); this );
    oo.inheritClass( Unicorn, Animal );
    oo.mixinClass( Unicorn, Magic );
}( OO ) );

Quick start

This library is available as an npm package! Install it right away:

npm install oojs

Or clone the repo, git clone

ECMAScript 5

OOjs is optimised for modern ECMAScript 5 environments. However, care has been taken to maintain parser compatibility with ES3 engines (such as for IE 6-8).

No ES5 syntax or unpolyfillable features are used. To support ES3 engines, ensure an appropriate polyfill is loaded before OOjs.

These are the methods used:

  • Array.isArray
  • Object.keys
  • JSON.stringify

Additionally, Object.create is used if available. As it is impossible to fully polyfill, OOjs includes a fallback implementing the minimal set of required features.

While there are no plans to ship a polyfill for remaining methods, we recommend the following and use them ourselves in the unit tests to assert support for older browsers.


If your project uses jQuery, use the optimised oojs.jquery.js build instead.

This build assumes jQuery is present and omits various chunks of code in favour of references to jQuery.

jQuery 1.8.3 or higher is recommended.


We use the Semantic Versioning guidelines as much as possible.

Releases will be numbered in the following format:


For more information on SemVer, please visit

Bug tracker

Found a bug? Please report it in the issue tracker!


Release process:

$ cd path/to/oojs/
$ git remote update
$ git checkout -B release -t origin/master

# Ensure tests pass
$ npm install && npm test

# Avoid using "npm version patch" because that creates
# both a commit and a tag, and we shouldn't tag until after
# the commit is merged.

# Update release notes
# Copy the resulting list into a new section on
$ git log --format='* %s (%aN)' --no-merges --reverse v$(node -e 'console.log(require("./package.json").version);')...HEAD
$ edit

# Update the version number
$ edit package.json

$ git add -p
$ git commit -m "Tag vX.X.X"
$ git review

# After merging:
$ git remote update
$ git checkout origin/master
$ git tag "vX.X.X"
$ git push --tags
$ npm publish