How to write component guard in vue page

Vue.js is a popular JavaScript framework designed for building interactive user interfaces. Vue has some very powerful and useful features, one of which is component guards. Component guards can be used to enhance the functionality of components and improve code readability and maintainability. Below we will learn how to write component guards in Vue.

What is a component guard?

In Vue.js, component guards are hook functions that are used to perform some operations at specific points in the component life cycle. Vue.js provides a number of different component guards, including "created", "mounted", "updated" and "destroyed". These guards allow you to perform various operations in your component, such as data retrieval, data processing, and component cleanup.

Writing component guards in Vue

It is very easy to use component guards in Vue. The following is a simple Vue component that contains all available component guards:

Vue.component('my-component', {
  data: function () {
    return {
      message: 'Hello Vue!'
    }
  },
  beforeCreate: function () {
    console.log('组件实例化之前执行');
  },
  created: function () {
    console.log('组件实例化完毕，属性计算之前执行');
  },
  beforeMount: function () {
    console.log('挂载开始之前执行');
  },
  mounted: function () {
    console.log('组件挂载完成，此时可以访问到DOM元素');
  },
  beforeUpdate: function () {
    console.log('数据更新之前执行');
  },
  updated: function () {
    console.log('数据更新完毕，此时可以访问到DOM元素');
  },
  beforeDestroy: function () {
    console.log('组件销毁之前执行');
  },
  destroyed: function () {
    console.log('组件销毁之后执行');
  },
  methods: {
    setMessage: function (newMessage) {
      this.message = newMessage;
    }
  }
})

In the above code, we define a Vue component and provide all available component guards. Each guard function is called at a specific time (from the beginning to the end of the component's lifecycle). For example, execute the "beforeCreate" guard before the component is instantiated, execute the "mounted" guard after the component is mounted, and so on.

When we create a Vue instance, these component guards will be called automatically. You can view the output in the console to better understand how the Vue component guard works.

Application scenarios of component guards

The main purpose of component guards is to perform operations during the component life cycle. For example, you might need to load some data before the component is created, or perform cleanup before the component is destroyed. The following are some common component guard application scenarios:

• beforeCreate: Executed before component instantiation, which can be used to set component properties or perform data initialization.
• created: Executed after component instantiation, but before computed properties and observer binding. This is a good place to initialize your data.
• mounted: Executed after the component is mounted to the DOM. This is a great place to access DOM elements or external plugins.
• beforeUpdate: Executed before data is updated. Here you can perform data processing or judgment logic.
• updated: Executed after the data is updated. This is a great place to manipulate the DOM or other external plugins.

Summary

Vue.js component guard is a very useful feature that can help us perform operations at specific times in the component life cycle. Vue.js provides a number of different component guards, including "created", "mounted", "updated" and "destroyed". These guards make writing Vue.js applications simpler, readable, and maintainable.

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