The function and principle of key in vue

The role of key in Vue is to track the unique identity of list elements to optimize update performance and ensure correct deletion. The principle is to use key as an identifier in the virtual DOM node and compare the old and new keys to update only the elements that have changed, or delete elements with different keys. Best practices include giving each element a unique key, using stable values ​​(such as IDs), and avoiding indexes.

The role and principle of key in Vue

In Vue.js, the key attribute is used to track the component list The unique identity of the element in . It is an important property that helps Vue optimize rendering performance and ensure correct updates and removals of components.

Function

The main functions of key are:

• Tracking element identity: key allows Vue to identify the list of each element, even if the content of the elements is the same.
• Optimized update: When the list is updated, Vue will compare the old and new keys so that only the changed elements are updated. This can improve rendering performance, especially when the list is large.
• Deleting elements: When deleting elements from the list, Vue uses key to identify the element to be deleted to ensure correct deletion.

Principle

key is actually an attribute that can be assigned to each element in the list. It is a unique identifier of an element in the virtual DOM. When Vue renders a list, it creates a unique virtual DOM node for each element and adds key as an attribute to that node.

When the list is updated, Vue will compare the new and old keys. If the keys are the same, Vue will reuse the old virtual DOM node and only update the necessary data. If the key is different, Vue will create a new virtual DOM node.

Best Practices

When using keys, there are the following best practices:

• Specify a unique value for each element in the list key.
• Use a value that is stable and does not change over time, such as an ID or unique identifier.
• Avoid using an index as a key because the index may change when the list is reordered.

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