Backbone.js Event listenTo()

The Backbone.js Event listenTo method tells an object to listen to a particular event on another object. It provides callback function when an event occurs and also keeps track of events.

Syntax:

Parameter explanation:

other: It is used to define the name of the other object.

event: It is used to bind an object.

callback: It is reference to the code and called with object as context.

Let's take an example.

See this example:

<!DOCTYPE html>
  <head>
    <title>Event listenTo Example</title>
      <script src="https://code.jquery.com/jquery-2.1.3.min.js" type="text/javascript"></script>
      <script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.8.2/underscore-min.js" type="text/javascript"></script>
      <script src="https://cdnjs.cloudflare.com/ajax/libs/backbone.js/1.1.2/backbone-min.js" type="text/javascript"></script>
  </head>
  <body>
     <script type="text/javascript">
     	//Create an object 'myVal' and 'myVal1' and extend them using Backbone.Events method
        var myVal = _.extend({name:'Hello..'}, Backbone.Events);
        var myVal1 = _.extend({name:'Welcome to JavaTpoint'}, Backbone.Events);
  //create the 'listenMe' callback function and invoke when one object listens to particular event on another object
        var listenMe = function(){
           document.write("The value is: ");
           document.write(this.name);
        };
      //The object 'myVal1' listens once for the 'listenMe' event triggered on object 'myVal'
       myVal1.listenTo(myVal, 'listenMe', listenMe);

       //The 'myVal' has no listenMe event and displays the value of 'myVal1'
       myVal.trigger('listenMe');
     </script>
  </body>
</html>

Test it Now

Output:

Save the above code in listento.html file and open this file in a browser.