When using the Backbone.js framework with model ``++defaults++`` that contain arrays or objects, ``++defaults++`` should be defined as a function rather than an object. This is because objects and arrays are passed by reference in JavaScript. So a ``++defaults++`` object that contains arrays or objects is going to set the default value of every instance to point to the same shared object or array.


Use a function instead and a fresh copy of the object or array will be peeled off for each instance.


== Noncompliant Code Example

----
var Person = Backbone.Model.extend({
    defaults: {  // Noncompliant; every instance of Person will share the same instance of favoriteColors
        favoriteColors: ["blue","purple","raspberry"]
    }
});
----


== Compliant Solution

----
var Person = Backbone.Model.extend({
    defaults: function() {
      return {
        favoriteColors: ["blue","purple","raspberry"]
      };
    }
});
----