[Solved-1 Solution] Event bubbling and capturing - javascript tutorial


What is the difference between event bubbling and capturing and Which one is the faster and better model to use ?

Solution 1:

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: trickle down, bubble up.

Back in the old days, Netscape advocated event capturing, while Microsoft promoted event bubbling. IE < 9 uses only event bubbling , whereas IE9+ and all major browsers support both. On the other hand, the performance of event bubbling may be slightly lower for complex DOMs. 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.



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.

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

var logElement = document.getElementById('log');

function log(msg) {
    logElement.innerHTML += ('<p>' + msg + '</p>');

function capture() {
    log('capture: ' + this.firstChild.nodeValue.trim());

function bubble() {
    log('bubble: ' + this.firstChild.nodeValue.trim());

var divs = document.getElementsByTagName('div');
for (var i = 0; i < divs.length; i++) {
    divs[i].addEventListener('click', capture, true);
    divs[i].addEventListener('click', bubble, false);
p {
    line-height: 0;

div {
    padding: 5px;

    background: #fff;
    border: 1px solid #aaa;
    cursor: pointer;

div:hover {
    border: 1px solid #faa;
    background: #fdd;
<section id="log"></section>

Event capturing

When we use event capturing

               | |
---------------| |-----------------
| element1     | |                |
|   -----------| |-----------     |
|   |element2  \ /          |     |
|   -------------------------     |
|        Event CAPTURING          |

The event handler of element1 fires first, the event handler of element2 fires last.

Event bubbling

When we use event bubbling

               / \
---------------| |-----------------
| element1     | |                |
|   -----------| |-----------     |
|   |element2  | |          |     |
|   -------------------------     |
|        Event BUBBLING           |

The event handler of element2 fires first, the event handler of element1 fires last.

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