As a Vue developer, we all know that when using the v-for directive to render a list in Vue, it must be in each child component. Add a key attribute. This key attribute is a special attribute used to identify the uniqueness of each node. There is a big difference between the key in the Vue2.x version and the key in the Vue3.x version, so in this blog , we will discuss the difference between key in Vue2 and key in Vue3.

key in Vue2

In the Vue2.x version, key Mainly used for optimization strategies in Vue’s virtual DOM algorithm. In Vue2, when using the v-for instruction to render a list, Vue will compare the old and new nodes based on the value of key, and then DOMUpdate. key in Vue2 has the following characteristics:

• key must be a string or numeric type, cannot be an object and array. [Related recommendations: vuejs video tutorial, web front-end development]

##The value of key must be unique and cannot be repeated.
The value of key must be predictable and
• cannot be

  randomly generated.

In

, due to the use of the key optimization strategy, DOM rearrangement and Re-rendering improves rendering performance and avoids erroneous data updates.

In the

version, the role of key is the same as Vue2.x# The in the ## version is different , it is mainly used to track the identity of the node . In Vue3, when using the v-for directive to render a list, Vue will determine which nodes are new based on the value of key Which nodes were added and deleted, and then the DOM was updated. key in Vue3 has the following characteristics:

including
• objects and arrays.
  The value of key must be unique and cannot be repeated.

• The value of key
can
• be non-predictable, such as a randomly generated value. The difference between

  key in

Vue3 and Vue2 is that the key in Vue3 is used for Keep track of node identity, rather than just optimizing rendering. This means that in Vue3, the uniqueness of key must be guaranteed, otherwise it will lead to node identity confusion, resulting in incorrect rendering results. This design is mainly to improve rendering efficiency and performance

Vue2, there may be some problems when dealing with dynamic lists. The reason

Vue2 just makes a simple judgment based on the key value, and then compares The difference between old and new nodes makes it impossible to accurately know which nodes are added and which nodes are deleted.

Vue3 solves these problems. Using

you can accurately determine which nodes are added and which nodes are deleted. This makes Vue3 more efficient and accurate when processing dynamic lists, avoiding some problems existing in Vue2. Therefore, designing key to track the identity of nodes is an important optimization for Vue3 in improving rendering efficiency and performance. Conclusion

key

and key# in Vue3 ##There is a big difference in usage. The key in Vue2 is mainly used to optimize rendering performance, while the key in Vue3 is mainly used to track the identity of the node. The key in Vue3 can be of any type, including objects and arrays, but uniqueness must be guaranteed. Whether we are using Vue2 or Vue3

key must be added when using the v-for instruction to render the list Attribute, this is to ensure the correctness of rendering. (Learning video sharing: vuejs introductory tutorial, Basic programming video

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