What is event bubbling commonly used for?

Event bubbling is often used in event delegation, dynamic addition of elements, event proxy, event cancellation and blocking, etc. Detailed introduction: 1. Event delegation is one of the important applications of the event bubbling mechanism. By registering the event handler on the parent element instead of each child element, event monitoring of a large number of child elements can be achieved, which can reduce Memory consumption and improved performance; 2. Add elements dynamically. When adding elements dynamically, if the event bubbling mechanism is not used, event handlers need to be manually registered for each newly added element, which will lead to code redundancy and so on.

The operating system for this tutorial: Windows 10 system, DELL G3 computer.

Event bubbling (Event Bubbling) means that in Web development, when an element triggers an event, the event will propagate to the parent element until it propagates to the top-level element. During propagation, you can register the same event handler on each parent element to respond differently to events. The event bubbling mechanism is an important concept in web development and is widely used in various scenarios.

Event bubbling is often used in the following aspects:

1. Event delegation: Event delegation is one of the important applications of the event bubbling mechanism. By registering event handlers on the parent element rather than on each child element, you can implement event listening for a large number of child elements. This reduces memory consumption and improves performance. For example, we can register a click event on the parent element of a list, and then perform different operations by determining which child element the event source is. This avoids adding event listeners to each child element.

2. Dynamically adding elements: When adding elements dynamically, if you do not use the event bubbling mechanism, you need to manually register event handlers for each newly added element. This will lead to code redundancy and difficulty in maintenance. Using the event bubbling mechanism, you only need to register the event handler on the parent element to take effect on all newly added child elements.

3. Event proxy: Event proxy is a more advanced application that combines the ideas of event bubbling mechanism and event delegation. Through the event proxy, you can listen to multiple different events on the parent element and perform corresponding operations based on the different event sources. Event proxies can simplify code logic and improve code maintainability and readability. For example, we can listen to mouse move-in and move-out events on a parent element, and then perform corresponding animation effects based on different event sources.

4. Cancellation and blocking of events: Through the event bubbling mechanism, you can easily cancel the default behavior of the event or prevent the further propagation of the event. In an event handler, you can use the event object's methods, such as `preventDefault()` and `stopPropagation()`, to cancel the event's default behavior or prevent the event from bubbling. This enables precise control of events and avoids unnecessary operations.

In short, the event bubbling mechanism plays an important role in Web development. It can simplify code logic and improve code maintainability and readability. By making reasonable use of the event bubbling mechanism, we can implement functions such as event delegation, dynamic addition of elements, event proxy, and event cancellation and blocking, bringing a better user experience to our web applications.

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