Question

Looking through Backbones source I noticed that classes are defined like this:

var Model = Backbone.Model = function(...

Why is Model defined twice I ask myself, a search for Model showed that the prototype of Model is then extended like so:

_.extend(Model.prototype, Events, {

I did a little test and it seems that if ‘Model.prototype’ is being extended the changes automatically affect Backbone.Model, what’s the reason behind this and why wasn’t it instead written written like this:

Backbone.Model = function(...
Backbone.Model.prototype.extend(...

Hopefully this will lift my understanding of prototypal inheritance up a notch

Answer 1

It’s just a shortcut to have a local variable named Model which is shorter to type than Backbone.Model. Javascript doesn’t have a concept of references so both Model and Backbone.Model point to the exact same object.