Vue is a popular front-end JavaScript framework that provides many instructions to simplify the data binding process. One of the very useful instructions is v-once. In this article, we will delve into the use of the v-once directive and how to implement data-bound one-time rendering in Vue.

What is the v-once instruction?

v-once is a directive in Vue. Its function is to cache the rendering results of elements or components so that their rendering process can be skipped in subsequent updates. This can greatly improve rendering performance, especially when the data does not change frequently.

The syntax for using the v-once directive is very simple. You only need to add this directive on the element or component that needs to be cached:

<template>
  <div v-once>
    {{ message }}
  </div>
</template>

In the above code, we give

Usage of v-once directive

In addition to using the v-once directive on a single element, it can also be used on components. Using the v-once directive in a component is the same as using it on an element, you just need to attach the directive to the root element of the component:

<template>
  <my-component v-once :data="data"></my-component>
</template>

In the code above, we have The v-once directive is used on the root element and an attribute called data is passed. This means that we only want to render the component once, and Vue will not re-render the component if the data property changes.

It should be noted that the v-once directive can only be used for static content, that is, content that does not contain binding expressions. This means that you cannot use interpolation syntax or other binding expressions inside an element or component when using the v-once directive.

Of course, there are some other uses of the v-once instruction, such as:

• Using the v-once instruction on elements within the v-for loop can greatly improve the list Rendering performance;
• Using the v-once directive in the template can cache the rendering results of the entire template for reuse in subsequent renderings.

How to implement one-time rendering of data binding in Vue

Now that we have understood the usage of the v-once directive, below we will demonstrate how to use this directive in Vue To achieve one-time rendering of data binding.

Suppose we have a user list component containing several user list items. When we click a button on a list item, the list item's status will change, for example, to a deleted status. At this time, we want the list item to disappear from the list, but at the same time, we want its status to remain for subsequent operations.

In order to achieve this function, we can use the v-once directive in the list item component:

<template>
  <li v-if="!deleted" v-once>
    {{ user.name }}
    <button @click="onDelete">刪除</button>
  </li>
</template>

<script>
export default {
  props: ['user'],
  data() {
    return {
      deleted: false
    };
  },
  methods: {
    onDelete() {
      this.deleted = true;
    }
  }
};
</script>

In the above code, we use v-once on the