Backbone.js Event listenToOnce()

Backbone.js Event listenToOnce method is same as listenTo event but the only difference that causes the listen to occur only once before the callback function is being removed.

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 listenToOnce 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:'SSSIT'}, Backbone.Events);
        var myVal1 = _.extend({name:'JavaTpoint'}, Backbone.Events);
 //created the 'listenMe' callback function and invoked when one object listen to particular event on another object
        var listenMe = function(){
           document.write("The value is: ");
           document.write(this.name);
        };

        //The object 'myVal1' listen once for the 'listenMe' event triggered on object 'myVal'
        myVal1.listenToOnce(myVal, 'listenMe', listenMe);

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

Test it Now

Output:

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