Best Practices for Using `key` in Vue.js: Ensuring Efficiency and Maintainability

Why Write key and What Does it Do?

The key attribute in the Vue framework is a special attribute used to help Vue track and manage the reuse and state of reusable elements.

In Vue, when you use the v-for directive to render an array, Vue will try to reuse existing elements as much as possible instead of recreating them. Vue uses the key attribute to identify the identity of each node so that it can update the virtual DOM more efficiently when the data changes.

When Vue is updating a rendered element list with v-for, it defaults to the "in-place reuse" strategy. If the order of the data items is changed, Vue will not move DOM elements to match the order of the data items, but will update each element in place and ensure that they can be reused without losing their state.

However, in some special cases, in-place reuse is not enough, and we need to provide a unique identifier for each item. This is the purpose of the key attribute. By providing a unique key for each element rendered by v-for, Vue can more accurately track the identity of each node, so that it can reorder elements or re-render the list when the data changes.

In general, the key attribute is an important attribute in Vue to help identify VNodes. It helps Vue accurately track the identity and state changes of each node when rendering lists efficiently.