What does event capture do?

The functions of event capture include conveniently obtaining target elements and contextual information, effectively preventing event bubbling, customizing event processing logic, and improving page response speed. Detailed introduction: 1. It is convenient to obtain the target element and contextual information. In the event capture phase, when an event occurs, the browser will start from the outermost element and search for elements associated with the event layer by layer until the target element is found. So far; 2. Effectively prevent event bubbling. In the event model, when an event occurs, it will be passed down layer by layer starting from the outermost element. This process is called event bubbling, etc.

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

Event capture is an event model that handles events in the event bubbling stage. It mainly has the following functions:

Conveniently obtain target elements and contextual information

In the event capture phase, when an event occurs, the browser will start from the outermost element and search for elements associated with the event layer by layer until the target element is found. In this process, each layer of elements will trigger the corresponding event handler. Developers can obtain the attributes, location and other information of the target element when the event occurs, as well as contextual information related to the target element in these event handlers. This information can be used for further processing and operations, such as determining the type and location of the target element. By passing the event object down layer by layer in the event capture phase, developers can obtain the contextual information of the event to facilitate more sophisticated and complex operations.

Effectively prevent event bubbling

In the event model, when an event occurs, it will be passed down layer by layer starting from the outermost element. This process is called event bubbling. If the developer wishes to prevent the event from bubbling, the event handler can cancel the event's default behavior and prevent the event from bubbling. By performing corresponding processing in the event capture phase, events can be effectively prevented from bubbling and unnecessary processing and operations can be avoided.

Customized event processing logic

Developers can customize event processing logic during the event capture phase. For example, when a user clicks a button, some preprocessing operations can be performed during the event capture phase, such as verifying user permissions, determining user identity, etc. If certain conditions are met, further processing of the event can be suspended, or some additional operations can be performed. This customized processing logic can expand event processing functions and improve development efficiency and flexibility. During the event capture phase, developers can flexibly design event processing processes and logic to meet actual needs.

Improve page response speed

In the event capture phase, developers can add some optimization strategies to the event handler, such as caching calculation results, avoiding unnecessary DOM operations, etc. These optimization strategies can increase page response speed and improve user experience. By optimizing event handlers and reducing unnecessary calculations and operations, you can speed up page response and improve user experience.

In general, event capture is a commonly used event processing model. By binding event processing functions layer by layer and executing corresponding event handlers in the capture phase, developers can better obtain and understand the contextual information in which events occurred to perform more sophisticated and complex operations. At the same time, it also provides custom event processing logic, effectively prevents event bubbling and improves page response speed. It is widely used in Web front-end development.

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