In vue: the role of key

The key attribute in Vue is used to uniquely identify list elements, helping Vue track element identity, update the DOM correctly, optimize performance, and avoid unnecessary re-rendering. Usage rules include: each element must have a unique and stable string, number, or symbol key; object lists can use the id attribute as the key, and array lists can be used but try to avoid using indexes as the key.

The role of key in Vue

In Vue, key attribute is a special attribute used to uniquely identify each item element in the list. Its main purpose is to optimize the rendering process of virtual DOM and improve performance and efficiency.

When to use key

It is critical to use key in the following situations:

• When the elements in the list have dynamically changing order or content.
• When elements in the list need to be tracked or updated.
• When the elements in the list contain interactive components or sub-elements.

Key Function

key The function of the attribute is as follows:

• Help Vue track the identity of list elements even if they are reordered or updated in the data.
• Ensure that Vue can correctly update the DOM when elements are updated.
• Avoid unnecessary DOM re-rendering to optimize performance.
• In conditional rendering or within a loop, key can also help Vue distinguish different subcomponents.

How to use key

When using key in a list, you need to follow the following rules:

• Each list element must have a unique and stable key.
• key The value should be a string, number, or symbol, but not a boolean or object.
• For object lists, the id attribute of the object is usually used as the key.
• For array lists, it is possible to use the array index as the key, but this is not recommended because the array index may change.

Example

The following code snippet demonstrates how to use key:

<code class="html"><template>
  <ul>
    <li v-for="item in items" :key="item.id">{{ item.name }}</li>
  </ul>
</template></code>

In this example, items is an array of objects, each object has a unique id attribute. Vue will use this id property as a key to keep track of the identity of each element in the list.

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