The principle of event bubbling and the event types it supports

Event bubbling (event bubbling) means that in front-end web development, when a specific event is triggered, the event will bubble up from the triggered element until it reaches The top-level parent element. This article will explore how event bubbling works and the types of events it supports.

The principle of event bubbling is based on the structure of the DOM tree. In a web page, the nested relationship of elements forms a hierarchical structure, which constitutes the DOM tree. When an event is triggered, the event will bubble up the DOM tree starting from the triggering element. That is to say, the event will trigger the event handler of the same event type bound to each ancestor element in turn.

During the event bubbling process, the event processing function bound to each element will be triggered in turn. The advantage of this is that it can simplify the event handling process. For example, if there are multiple button elements in a web page, each button is bound to the same click event handler. When any button is clicked, the click event will bubble up to the parent element, thereby triggering the event handler bound to the parent element, without having to write an independent click event handler for each button.

Event bubbling supports multiple event types. The following are some common event types:

1. Click event (click): triggered when the user clicks an element. The click event bubbling method can easily realize functions such as switching, expanding and contracting the click state of elements.
2. Mouse in and out events (mouseover and mouseout): Triggered when the mouse moves in or out of an element. These events are often used to achieve effects such as floating prompt boxes and drop-down menus.
3. Keyboard events (keydown, keyup and keypress): Triggered when the user presses or releases a keyboard key. Keyboard event bubbling can easily implement keyboard shortcuts and other functions.
4. Form event (submit): Triggered when the user submits a form. The form event bubbling method can easily implement functions such as form verification and data verification.
5. Element size change event (resize): Triggered when the size of the element changes. This event is often used to respond to window size changes and is very useful in page layout.
6. Clipboard events (copy, cut and paste): Triggered when the user copies, cuts or pastes content. The way these events bubble up makes it easy to implement custom copy, cut, or paste operations.

In addition to the event types listed above, there are many other types of events that also support bubbling. In actual development, appropriate event types can be selected for binding and processing according to specific needs.

Although event bubbling facilitates the work of developers, it sometimes causes some problems. If multiple event handlers of the same type are bound to an ancestor element, multiple handlers may be executed at the same time. At this time, you need to pay attention to the execution order of event processing functions, which can be solved by adjusting the order of binding event processing functions.

In short, event bubbling is an important mechanism in front-end web development. It simplifies the event processing process and improves development efficiency through event delivery and bubbling. Understanding the principle of event bubbling and supported event types will help developers better use and process events and achieve rich and diverse interactive functions.

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