Question

In http://addyosmani.github.com/backbone-fundamentals/, it is said that

every single one of the following objects inherits from Backbone.Events:

Backbone.Model
Backbone.Collection
Backbone.Router
Backbone.History
Backbone.View

and I can also find in backbone.js the following:

// Attach all inheritable methods to the Model prototype.
_.extend(Model.prototype, Events, {  ....

However, I tried to check for the inheritance, by

Backbone.Model.prototype.__proto__ === Backbone.Events

in Firebug, and it shows false, and

Backbone.Model.prototype.__proto__.__proto__

is already null, meaning the end of the prototype chain. So how can the inheritance be shown?

Answer 1

The page you’re referencing is incorrect, nothing in Backbone inherits from Backbone.Events. However, Backbone.Events is mixed into the other Backbone “classes”. The bit of code you mention:

_.extend(Model.prototype, Events, { ...

is not setting up inheritance, it is simply mixing Events into Model‘s prototype and the effect is similar to this:

for k in Events
    Model.prototype[k] = Events[k]

so it is simply add Events‘s methods to Model. The Backbone document only says this:

Backbone.Events

Events is a module that can be mixed in to any object, giving the object the ability to bind and trigger custom named events.

Note the mixed in terminology.

Backbone.Events isn’t even a constructor function (it is simply an object) so there’s nothing to inherit from.