Backbone.js once Event
Last Updated :
06 Jul, 2022
Backbone.js Once Event is used to bind a callback function to an object, i.e invoked only once when an event is triggered before it is removed. In this type of event triggering, the callback is invoked only once for every event passed to it.
Syntax:
object.once(event, callback, [context] )
If there are a large number of events on a page then the convention is to use colons “: ” in order to namespace each event.
example:"change:selection"
Parameter Values:
- event: It is used to bind an object with an event.
- callback: It is executed when an event is triggered.
- context: It is an object which can be passed to the callback function.
Example 1: This example describes the once event in Backbone.js.
HTML
<!DOCTYPE html>
<head>
<title>Backbone.js Once Event</title>
<script src=
type="text/javascript">
</script>
<script src=
type="text/javascript">
</script>
<script src=
type="text/javascript">
</script>
</head>
<body>
<h1 style="color: green;">
GeeksforGeeks
</h1>
<h3>Backbone.js Once event</h3>
<script type="text/javascript">
var obj = {};
_.extend(obj, Backbone.Events);
obj.once('trigger', function() {
document.write(
'<h2 style="color:blue;">OUTPUT AFTER TRIGGERING ONCE EVENT:</h2>');
alert("triggered");
});
obj.trigger('trigger');
obj.trigger('trigger');
</script>
</body>
</html>
|
Output:
Backbone.js Once event
Example 2: This example describes the Backbone.js Once event for multiple events
HTML
<!DOCTYPE html>
<head>
<title>Backbone.js Once Event</title>
<script src=
type="text/javascript">
</script>
<script src=
type="text/javascript">
</script>
<script src=
type="text/javascript">
</script>
</head>
<body>
<h1 style="color: green;">
GeeksforGeeks
</h1>
<h3>Backbone.js Once event</h3>
<script type="text/javascript">
var Value = _.extend({
name: 'GeeksforGeeks'
}, Backbone.Events);
Value.once('HelloWorld', function() {
document.write("The value after invoking first event is: ");
document.write(this.name);
});
Value.once('second', function() {
document.write("<br>");
document.write(
"The value after invoking second event is: GeeksforGeeks + ");
document.write(this.name);
});
Value.trigger('HelloWorld');
Value.trigger('second');
</script>
</body>
</html>
|
Output:
Backbone.js Once event with multi-event
Reference: https://backbonejs.org/#Events-once
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