.delegate()

delegate ( selector, eventType, handler(eventObject) ) Returns: jQueryversion added: 1.4.2

  • selector
    Type: String
    A selector to filter the elements that trigger the event.
  • eventType
    Type: String
    A string containing one or more space-separated JavaScript event types, such as "click" or "keydown," or custom event names.
  • handler(eventObject)
    Type: Function
    A function to execute at the time the event is triggered.

delegate ( selector, eventType, eventData, handler(eventObject) ) Returns: jQueryversion added: 1.4.2

  • selector
    Type: String
    A selector to filter the elements that trigger the event.
  • eventType
    Type: String
    A string containing one or more space-separated JavaScript event types, such as "click" or "keydown," or custom event names.
  • eventData
    Type: Object
    An object containing data that will be passed to the event handler.
  • handler(eventObject)
    Type: Function
    A function to execute at the time the event is triggered.

delegate ( selector, events ) Returns: jQueryversion added: 1.4.3

  • selector
    Type: String
    A selector to filter the elements that trigger the event.
  • events
    Type: PlainObject
    A plain object of one or more event types and functions to execute for them.

Description: Attach a handler to one or more events for all elements that match the selector, now or in the future, based on a specific set of root elements.

As of jQuery 1.7, .delegate() has been superseded by the .on() method. For earlier versions, however, it remains the most effective means to use event delegation. More information on event binding and delegation is in the .on() method. In general, these are the equivalent templates for the two methods:


// jQuery 1.4.3+
$( elements ).delegate( selector, events, data, handler );
// jQuery 1.7+
$( elements ).on( events, selector, data, handler );

For example, the following .delegate() code:


$( "table" ).delegate( "td", "click", function() {
  $( this ).toggleClass( "chosen" );
});

is equivalent to the following code written using .on():


$( "table" ).on( "click", "td", function() {
  $( this ).toggleClass( "chosen" );
});

To remove events attached with delegate(), see the .undelegate() method.

Passing and handling event data works the same way as it does for .on().

Examples:

Example: Click a paragraph to add another. Note that .delegate() attaches a click event handler to all paragraphs - even new ones. 

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <title>css demo</title>

  <style>

  p {
    background: yellow;
    font-weight: bold;
    cursor: pointer;
    padding: 5px;
  }
  p.over {
    background: #ccc;
  }
  span {
    color: red;
  }

  </style>

  <script src="//code.jquery.com/jquery-1.10.2.js"></script>
</head>
<body>
  

<p>Click me!</p>

<span></span>

<script>

$( "body" ).delegate( "p", "click", function() {
  $( this ).after( "<p>Another paragraph!</p>" );
});

</script>

  
</body>
</html>

Demo:

Example: To display each paragraph's text in an alert box whenever it is clicked: 

$( "body" ).delegate( "p", "click", function() {
  alert( $( this ).text() );
});

Example: To cancel a default action and prevent it from bubbling up, return false: 

$( "body" ).delegate( "a", "click", function() {
  return false;
});

Example: To cancel only the default action by using the preventDefault method. 

$( "body" ).delegate( "a", "click", function( event ) {
  event.preventDefault();
});

Example: Can bind custom events too. 

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <title>css demo</title>

  <style>

  p {
    color: red;
  }
  span {
    color: blue;
  }

  </style>

  <script src="//code.jquery.com/jquery-1.10.2.js"></script>
</head>
<body>
  

<p>Has an attached custom event.</p>
<button>Trigger custom event</button>
<span style="display:none;"></span>

<script>

$( "body" ).delegate( "p", "myCustomEvent", function( e, myName, myValue ) {
  $( this ).text( "Hi there!" );
  $( "span" )
    .stop()
    .css( "opacity", 1 )
    .text( "myName = " + myName )
    .fadeIn( 30 )
    .fadeOut( 1000 );
});
$( "button" ).click(function() {
  $( "p" ).trigger( "myCustomEvent" );
});

</script>

  
</body>
</html>

Demo: