BackboneJS - Event listenToOnce

Description

It is the same like the listenTo event, but causes the listento to occur only once before the callback function is being removed.

Syntax

object.listenToOnce(other, event, callback)

Parameters

other − It defines name of the other object.
event − It binds an object.
callback − It is reference to the code and called with object as context.

Example

Live Demo

<!DOCTYPE html>
<html>
   
   <head>
      <title>Event Once 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:'Saurav Ganguly'}, Backbone.Events);
         var myVal1 = _.extend({name:'Sachin Tendulkar'}, 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>

Output

Let us carry out the following steps to see how the above code works −

Save the above code in listentoonce.htm file.
Open this HTML file in a browser.

backbonejs_events.htm