Backbone.js LogoIn the previous post: “Getting Started with Backbone.js Models – Introduction,” I discussed how the extend method of the Backbone.Model constructor is extended, which results in a new “class” that you can instantiate. When extending this constructor, an object was passed-in, which contained default values for the model data. Those default values were key/value pairs that were contained in the “defaults” property of the passed-in object.

In this post, we will talk about a sibling the of “defaults” property: the “Initialize” method.

The “Initialize” method

Why would we care about an Initialization method? Single page applications require an intimate relationship with the data. Not only do you consume and present data, but in many cases, you will want to know when a Backbone model is created or changed. Adding an “Initialize” method to your Backbone model allows you to interact with your model at the time of creation.

Why would I need an “Initialize” method?

While there are many answers to that question, a fairly typical one would be: “notification.” Let’s say that your single page application (aka “spa”), consumes a list of salespeople who work for a company, and presents that list in the DOM. If the application allows the user to create a new salesperson, then you would likely want to update the DOM, adding the new salesperson to the list. The most logical way to accomplish this is to have a method attached to your model that executes when a new instance is created (i.e. when the model constructor is instantiated), and that initialize method would update the DOM, possibly even presenting the data from this new model.

NOTE: In order to keep the code examples here short and simple, I will only present code that has changed since the last post. For the base code that is behind the working example below, view the page source as well as the link to the JavaScript file.

Example # 1A

Example # 1B

In Example # 1A, we have a quick re-cap of or SalesPerson Backbone model from the previous post. As discussed, we extend the Backbone.Model constructor, passing-in an object with a “defaults” property, which contains key/value pairs that supply default data values (e.g. “John” and “Smith”).

In Example # 1B, we have added a method named: “Initialize”. This method is executed when the model is instantiated. This means that every time we create a new model, that model’s “Initialize” method will execute. In this example, a message is logged to the console, which includes the “fname” and “lname” properties.


(be sure to open your JavaScript console when you view the JS Fiddle link above)

Example # 2



In Example # 2, we have the actual code from the full working example (link below). The reason for the setTimeout is to exaggerate the “message” effect. Since things happen pretty quickly, I wanted to make it a bit easier to see that when a new model is created, that model’s “initialize” method executes.


How to Demo:

Each time a new SalesPerson item is created, a green message flashes in the upper-left-hand corner of the browser. When the page loads, there are four such messages. As you manually add new SalesPerson items, a green message will flash, showing the model data. All of this is made possible by the SalesPerson constructor’s initialize method.


In this post, we learned how to create an initialize method for a Backbone Model. We discussed why this is important, and how it can be used in a real-world context.

Helpful Links for Backbone Model’s initialize method