In-depth understanding of Vue's component life cycle

In-depth understanding of Vue’s component life cycle requires specific code examples

Introduction:
Vue.js is a progressive JavaScript framework that is simple and easy to learn. , efficient and flexible features and are favored by developers. In the component development of Vue, understanding the life cycle of components is an important part. This article will delve into the life cycle of Vue components and provide specific code examples to help readers better understand and apply them.

1. Life cycle diagram of Vue component
The life cycle of Vue component can be seen as the entire process from creation to destruction of the component. The figure below is a life cycle diagram of a Vue component, including hook functions at different stages. When a component is created, it will go through the "creation phase", "mounting phase", "update phase" and "destruction phase" in sequence.

(Insert life cycle icon)

2. Specific stages and hook functions of Vue component life cycle

1. Creation phase(Creation)

   • beforeCreate: Called after instance initialization and before data observer and event/watcher event configuration. At this time, the data and events in the component have not yet been initialized.
   • created: Called after the instance is created. At this point, the data in the component can already be accessed, and operations such as data initialization can be performed.

2. Mounting phase (Mounting)

   • beforeMount: Called before the template is rendered into HTML. At this point, the template has been compiled but has not yet been mounted on the page.
   • mounted: Called after the template is rendered into HTML. At this point, the component has been mounted to the page and DOM operations can be performed.

3. Updating phase (Updating)

   • beforeUpdate: Called before the responsive data changes and the virtual DOM is re-rendered. At this point, the data in the component has changed, but the DOM has not yet been updated.
   • updated: Called after the virtual DOM is re-rendered and patched. At this time, the component's data has been updated, and the DOM has also been updated.

4. Destruction phase (Destruction)

   • beforeDestroy: Called before the instance is destroyed. At this point, the component has not been destroyed and the component's data and methods can still be accessed.
   • destroyed: Called after the instance is destroyed. At this point, the component has been destroyed and the component's data and methods can no longer be accessed.

3. Code example

<template>
  <div>
    <p>组件生命周期示例</p>
    <p>{{ message }}</p>
  </div>
</template>

<script>
export default {
  data() {
    return {
      message: 'Hello, Vue!'
    }
  },
  beforeCreate() {
    console.log('组件创建阶段：beforeCreate')
  },
  created() {
    console.log('组件创建阶段：created')
  },
  beforeMount() {
    console.log('组件挂载阶段：beforeMount')
  },
  mounted() {
    console.log('组件挂载阶段：mounted')
  },
  beforeUpdate() {
    console.log('组件更新阶段：beforeUpdate')
  },
  updated() {
    console.log('组件更新阶段：updated')
  },
  beforeDestroy() {
    console.log('组件销毁阶段：beforeDestroy')
  },
  destroyed() {
    console.log('组件销毁阶段：destroyed')
  }
}
</script>

The above code is a simple Vue component example. At different life cycle stages, we use console output to view the execution of the hook function. You can run the example through the following steps:

1. Create a Vue project and introduce the above component files.

2. Use the above component in the parent component:

   <template>
     <div>
    <child-component></child-component>
     </div>
   </template>
   
   <script>
   import ChildComponent from '@/components/ChildComponent.vue'
   
   export default {
     components: {
    ChildComponent
     }
   }
   </script>

3. Run the project, view the console output, and observe the life cycle of the component.

By running the example, we can clearly see the execution sequence of the component's life cycle hook functions in different stages, and then gain an in-depth understanding of the life cycle of the Vue component.

Conclusion:
The life cycle of Vue components is an important concept in Vue, which is very helpful for understanding the creation, destruction and update process of Vue components. Through the introduction and sample code of this article, readers can have a deeper understanding of the life cycle of Vue components and flexibly apply them in actual development.

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