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Presumptionless model relations for Backbone in < 1kb.

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Use Backbone.associate to define relationships between application models and collections.

var Flag = Backbone.Model.Extend({ /* ... */ }),
    City = Backbone.Model.Extend({ /* ... */ }),
    Cities = Backbone.Collection.extend({ model: City }),
    Country = Backbone.Model.Extend({ /* ... */ });
Backbone.associate(Country, {
  flag: { type: Flag },
  cities: { type: Cities, url: '/cities' }

Here, we're associating a model (Country) with two relations: a Flag model and a collection of Cities. The association keys can be anything, but they should match the keys used in the data that will be passed into the application's parse method.

var canada = new Country({
  url: '/countries/canada',
  flag: {
    colors: ['red','white']
  cities: [
    { name: 'Calgary' },
    { name: 'Regina' }

When it's time to sync the parent resource back up with the server, child resources can be serialized and included in the request.

canada.toJSON(); // { flag: { colors: ['red','white'] }, ... 

Since associates are just attributes, they may be accessed at any time using the usual get.

// GET /countries/canada/cities 

For the truly lazy, associate provides a convenient accessor for each association:

canada.flag().set({ colors: ['red','white'] });
  { name: 'Edmonton' },
  { name: 'Montreal' },
  { name: 'Ottawa' },
  { name: 'Vancouver' }

That's handy for manipulating the relations, setting up eventing, or any of the many other things this plugin won't do for you. Speaking of which,

Things this plugin won't do...

...include making any but the most basic presumptions about how it will be used. Fortunately, all of these can be implemented as needed (fiddle here):

Identity mapping

var getCountry = function (id) {
  _countries = {};
  return (getCountry = function (id) {
    if (!_countries[id]) {
      _countries[id] = new Country({ id : id });
    return _countries[id];

Child events

canada.onCityAdded = function (model) {
  console.log('city added!', model.get('name'));
canada.listenTo(canada.cities(), 'add', canada.onCityAdded);


Specs are implemented with jasmine-node. After cloning this repo, install dependencies and test with npm.

$ npm install
$ npm test

Related projects

Looking for a more fully-featured alternative? Check out:


Backbone.associate is released under the terms of the MIT license