What's the difference between initialize and constructor on a backbone model

Question

What's the difference between initialize and constructor on a backbone model.

When I extend a backbone model (ParentModel) I use the initialize method to set any default properties. But whenever I create a Model based on the ParentModel I use the constructor to to run any intial functionality. I do this because it works but someone at work asked me why I use both initialize and constructor and I didn't have a good answer apart from it works. I could spend time reading though the source code to figure it out but it seemed much easier to ask here and get the right answer.

var ParentModel = Backbone.Model.extend({
  initialize : function() {
    // code here
  },
});


var Model = ParentModel.extend({
  constructor : function (options) {
    Backbone.Model.prototype.constructor.call(this, options);
    // code here
   },

Be aware that, just as your constructor() calls the base constructor(), your override of initialize() should start (at least in the case where you are using this pattern to extend what may already be an extended model) with <base>.initialize.apply(this, arguments);, to allow any base-defined initialize() to run first. (This caught me out in JointJS, which already has its own initialize() defined on certain of its own derived models.) — JonBrave

Boyo Boyo · Accepted Answer · 2012-04-12T07:32:15

constructor runs before Backbone sets up the structure. initialize is called inside the structure's constructor function. So basically if you need to augment anything before Backbone sets up the structure, use constructor if you need to augment anything after Backbone sets up the structure use initialize.

(from a Github discussion on the subject)

What's the difference between initialize and constructor on a backbone model

2 Answers