Backbone.js on Event

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Backbone.js on Event is used to bind a callback function to an object. When an event is triggered, the callback is invoked. If there are large numbers of events on a page then the convention is to use colons to namespace each event:

"poll:start", or "change:selection"

Syntax:

object.on(event, callback, [context] );

Callbacks that are bound to a special event “all” is triggered whenever any event occurs and the name of the event is passed as the first argument.

For example:

example.on("all", function(eventName) {  
    object.trigger (eventName);  
});

Parameter Values:

event: It is used to bind an object with an event.
callback: It is executed when an event is invoked.
context: It is an object which is passed to a callback function.

Example 1: This example describes the Backbone.js on Event.

HTML

<!DOCTYPE html> 
  
<head> 
    <title>Backbone.js On Event</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> 
    <h1 style="color: green;"> 
        zambiatek 
    </h1> 
    <h3>Backbone.js On event</h3> 
    <script type="text/javascript"> 
        var obj = {}; 
        _.extend(obj, Backbone.Events); 
        var counter = 0; 
        obj.on('trigger', function() { 
            counter++; 
            document.write( 
    '<h2 style="color:blue;">OUTPUT AFTER TRIGGERING ON EVENT :</h2>'); 
            document.write(counter); 
            alert("triggered"); 
        }); 
        obj.trigger('trigger'); 
        obj.trigger('trigger'); 
    </script> 
</body> 
</html>

Output:

Example 2: This example describes Backbone.js on Event specifying the multiple events.

HTML

<!DOCTYPE html> 
<html> 
  
<head> 
    <title>Backbone.js on event</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> 
    <h1 style="color: green;"> 
        zambiatek 
    </h1> 
    <h3>Backbone.js On event</h3> 
    <script type="text/javascript"> 
        var value = _.extend({ 
            name: 'zambiatek' 
        }, Backbone.Events); 
        value.on('first', function() { 
            document.write("Trigger-1) The triggered value is: "); 
            document.write(this.name); 
        }); 
        value.on('second', function() { 
            document.write("<br>"); 
            document.write("Trigger-2) The triggered value is: "); 
            document.write(this.name); 
        }); 
        value.trigger('first'); 
        value.trigger('second'); 
    </script> 
</body> 
</html>

Output:

Reference Link: https://backbonejs.org/#Events-on

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