What is event bubbling and capturing

http://stackoverflow.com/questions/4616694/what-is-event-bubbling-and-capturing

http://www.quirksmode.org/js/events_order.html#

http://javascript.info/tutorial/bubbling-and-capturing#

http://bitovi.com/blog/2010/10/a-crash-course-in-how-dom-events-work.html#

Event bubbling and capturing are two ways of event propagation in the HTML DOM API, when an event occurs in an element inside another element, and both elements have registered a handle
for that event. The event propagation mode determines in which
order the elements receive the event.

With bubbling, the event is first captured and handled by the innermost element and then propagated to outer elements.

With capturing, the event is first captured by the outermost element and propagated to the inner elements.

Capturing is also called "trickling", which helps remember the propagation order:

bubble up, trickle down

Back in the old days, Netscape advocated event capturing, while Microsoft promoted event bubbling. Both are part of the W3C Document
Object Model Events standard (2000).

IE < 9 uses only
event bubbling, whereas IE9+ and all major browsers support both.

We can use the 

addEventListener(type,
listener, useCapture)

 to register event handlers for in either bubbling (default) or capturing mode. To use the capturing model pass the third argument as 

true

.

Only the bubbling model is supported by all major browsers. If you are going to use event
capturing anyway, you need to handle event bubbling for IE. This makes it event bubbling easier to use, in that it provides wider browser compatibility. On the other hand, the performance
of event bubbling may be slightly lower for complex DOMs.

Example

<div>
   <ul>
       <li></li>
   </ul></div>

[/code]

In the structure above, assume that a click event occurred in the 

li

 element.

In capturing model, the event will be handled by the 

div

 first
(click event handlers in the 

div

 will
fire first), then in the 

ul

,
then at the last in the target element, 

li

.

In the bubbling model, the opposite will happen: the event will be first handled by the 

li

,
then by the 

ul

,
and at last by the 

div

 element.

For more information, see

Event
Order on QuirksMode

addEventListener on
MDN

Events
Advanced on QuirksMode

In the example below, if you click on any of the highlighted elements, you can see that the capturing phase of the event propagation flow occurs first, followed by the bubbling phase.

var divs = document.getElementsByTagName('div');function capture() {
   log('capture: ' + this.firstChild.nodeValue.trim())
}function bubble() {
   log('bubble: ' + this.firstChild.nodeValue.trim())
}for (var i = 0; i < divs.length; i++) {
   divs[i].addEventListener('click', capture, true);
   divs[i].addEventListener('click', bubble, false);
}var $log = $('#log');function log(msg) {
   $log.append('<p>' + msg + '</p>');
}

[/code]

div {
   border: 1px solid red;
   padding: 5px;
   min-height: 10px;
}

[/code]

<script src="http://code.jquery.com/jquery.min.js"></script><div>1
   <div>2
       <div>3
           <div>4
               <div>5</div>
           </div>
       </div>
   </div></div><section id="log"></section>

[/code]