Vue changes value and prohibits triggering

In Vue.js, through two-way data binding, when the data of the component changes, the component will be re-rendered, but sometimes we do not want some data changes to trigger re-rendering. This article will introduce how to prohibit Vue changes Value triggers re-rendering.

The data in Vue is responsive

The data in the Vue framework is responsive. This means that when data is changed, Vue will re-render the new data in the view. This feature makes page development easier and smoother.

For example, when the data changes, the following Vue component will automatically re-render:

<template>
  <div>
    <p>{{ message }}</p>
    <button @click="changeMessage">Click me to change message</button>
  </div>
</template>

<script>
export default {
  data() {
    return {
      message: "Hello world",
    };
  },
  methods: {
    changeMessage() {
      this.message = "Hello Vue.js";
    },
  },
};
</script>

In the above code, message is Vue's responsive data, but every time the Change Message button is clicked Causes the entire component to re-render, which may impact performance. Here's how to avoid this.

Use the $forceUpdate method

Vue provides a component method $forceUpdate() that can force the component to re-render. However, the $forceUpdate() method does not deeply trigger re-rendering. This means that if you change a piece of data, Vue will only re-render the component and subcomponents that contain that data.

If you call $forceUpdate() during the component rendering cycle, the component will re-render the entire component, even if the data has not changed. Therefore, we can prevent the component from rendering by calling the $forceUpdate() method when the data changes. For example:

<template>
  <div>
    <p>{{ message }}</p>
    <button @click="changeMessage">Click me to change message</button>
  </div>
</template>

<script>
export default {
  data() {
    return {
      message: "Hello world",
    };
  },
  methods: {
    changeMessage() {
      this.message = "Hello Vue.js";
      this.$forceUpdate();
    },
  },
};
</script>

In the above example, we called the $forceUpdate() method while modifying the data message. In this way, Vue will only re-render the component without affecting the performance of other components.

Using the vue-set method

Vue provides a vue-set method that can add or update a new responsive property to an object. This method is usually used to add new dom elements, or control some elements that do not need to be displayed in the Vue cycle. Using vue-set can avoid performance problems caused by repeated calls to forceUpdate:

<template>
  <div>
    <p>The message start with "{{ message.charAt(0) }}"</p>
    <button @click="prependChar">Click me to add new char</button>
  </div>
</template>

<script>
import {set} from 'vue'

export default {
  data() {
    return {
      message: "Hello world",
    };
  },
  methods: {
    prependChar() {
      const newChar = String.fromCharCode(
        this.message.charCodeAt(0) + 1
      );
      set(this.message, 0, newChar);
    },
  },
};
</script>

In the above code, when we click the button, new characters are added to the beginning of the message, and the set method is used to notify Vue to add A new reactive property so that performance issues with the forceUpdate method can be avoided.

Final Thoughts

In Vue, changing the responsive data will trigger the re-rendering of the component, which can make our development smoother. But sometimes we need to reduce the number of re-renders to improve page performance. In this article we introduced how to prevent component rendering by calling the $forceUpdate method and the vue-set method. At the same time, we need to pay attention to performance issues and code efficiency, and choose an appropriate method to implement the function of prohibiting value change triggering.

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