Event Bubbling vs. Capturing: When Should You Use Each Propagation Method?

Event Bubbling and Capturing: A Detailed Explanation

Event propagation in the HTML DOM API can take two forms: event bubbling and event capturing. The propagation mode determines the order in which events are received by elements nested within each other.

Event Bubbling

With event bubbling, events first occur in the innermost element and then propagate outward to its parent elements. This means that the innermost element receives the event first, followed by its parent, grandparent, and so on.

Event Capturing

In contrast to bubbling, event capturing propagates events inward, starting with the outermost element and moving towards the innermost element. This means that the outermost element receives the event first, before it reaches its child elements.

When to Use Bubbling vs Capturing

The choice between bubbling and capturing depends on the specific usage scenario:

• Bubbling: Ideal when you want to handle events in parent elements after they have occurred in child elements, allowing for more granular event management.
• Capturing: Useful when you want to intercept events before they reach inner elements, providing a way to stop the propagation of events or perform other actions before the target element handles them.

Example

Consider the following HTML structure:

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

If a click event occurs on the li element:

• Bubbling: The click event will propagate outward, first to the ul element and then to the div element.
• Capturing: The click event will propagate inward, first to the div element and then to the ul and li elements.

Browser Support and Performance

Internet Explorer 9 and above, as well as all major browsers, support both bubbling and capturing. However, in complex DOM structures, bubbling may be less performant.

To register event handlers using capturing, pass true as the third argument to addEventListener.

Additional Resources

• [Event Order on QuirksMode](https://www.quirksmode.org/js/events_order.html)
• [addEventListener on MDN](https://developer.mozilla.org/en-US/docs/Web/API/EventTarget/addEventListener)
• [Events Advanced on QuirksMode](https://www.quirksmode.org/js/events_advanced.html)

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