Access property of model on change event in backbone.js

Question

Just started Backbone.js and following tuorials at backbonejs.org.

Here is what I wanted to achieve. I created a model which asks for width and saves it. Now I have used listenTo with object I have created as below on model to read the changed property value. It triggered the change event , but, I always get undefined for width. Code is below.

var mod = Backbone.Model.extend({
    askColor:function() {
        var w = prompt("Enter width");
        this.set({ width:w})
    }
});

var model = new mod();
model.set({width:1234})

var obj = {};
_.extend(obj,Backbone.Events);
obj.listenTo(model, 'change', function() {
    alert("width = "+model.width)
})
model.askColor();

I really don't know what am I missing in the code or am I doing wrong? Please help out a beginner....

Answer 1

The width attribute is actually stored inside model.attributes . You should use .get() to get the width attribute.

obj.listenTo(model, 'change', function() {
    alert("width = "+model.get('width'))
})

Answer 2

You can also use model.attributes.width alongwith model.get('width') .

Also following is the best tutorial I found when I started to learn Backbone.js : http://adrianmejia.com/blog/2012/09/11/backbone-dot-js-for-absolute-beginners-getting-started/