Introduction to updated lifecycle functions in Vue documentation

Vue is a front-end framework that uses componentization to provide us with a very convenient development experience. In the development of Vue, life cycle function is a very important concept. Lifecycle functions are a set of hook functions in Vue, which are used to control some operations during the creation, mounting, updating, and destruction of instances. Among them, the updated life cycle function is a very important function in Vue. Next, we will introduce its related knowledge in detail.

1. Overview of the updated life cycle function

The updated life cycle function is a hook function in Vue, which is used to perform some operations after the component is updated. Normally, after the data in the component changes, the component will be re-rendered, and the updated hook function will be triggered.

2. The timing of calling the updated life cycle function

The timing of calling the updated life cycle function is after the DOM of the component has been updated. When Vue detects that the data in the component has changed, it will re-render the DOM structure of the component. After the DOM update is completed, the updated hook function will be triggered.

3. Syntax of the updated life cycle function

The syntax of the updated life cycle function in the Vue component is as follows:

updated() {
// In the updated function The operations
}

updated life cycle function can contain some operations. These operations can be some DOM operations, some data update operations, etc. These operations are all executed after the component update is completed.

4. Usage scenarios of the updated life cycle function

The updated life cycle function is usually used for some operations that need to be performed after the component update is completed, such as page data refresh and rebinding events. wait. In the actual development of Vue, we can implement some advanced operations through updated hook functions, such as:

1. Synchronous operations

In Vue, some operations may Will cause data changes, such as asynchronous requests, DOM operations, etc. If we need to perform certain operations after the data update is completed, we can choose to call these operations in the updated hook function to ensure that they can be executed after the data is updated.

2. Re-render the component

When we need to re-render a component, we can use the $forceUpdate() method in the updated hook function to force the component to be re-rendered . The $forceUpdate() method will re-call the render function and generate a new VNode node, and then compare the old and new VNode nodes to update the DOM tree.

3. Scroll position restoration of the component

In Vue, when we scroll the page in the component, if the component is re-rendered, the scroll position will be reset. At this time, we can cache the scroll position in the updated hook function and reset the scroll position after the component is re-rendered to maintain the continuity of page scrolling.

5. Precautions for the updated life cycle function

When using the updated life cycle function, we need to pay attention to the following points:

1. Do not use the updated hook function Modifying data in the component will cause the component to re-render infinitely, causing performance issues.
2. When operating the DOM in the updated hook function, we need to pay attention to whether the DOM has been rendered. You can use the nextTick function provided by Vue to wait for the DOM rendering to complete before performing operations.
3. When using the updated hook function, you need to be careful not to trigger the component update process frequently, because this will have a great impact on performance.

To sum up, the updated life cycle function is a very important hook function in Vue. It can help us perform some advanced operations after the component update is completed. When using the updated hook function, we need to pay attention to some precautions to ensure the performance and reliability of the code.

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