---
title: 生命周期
date: 2020-02-04 15:06:59
permalink: /pages/176808a1b5f843b8
categories:
  - 《Vue》笔记
  - 基础
tags:
  - Vue
author:
  name: xugaoyi
  link: https://github.com/xugaoyi
---
# 实例生命周期钩子

[实例生命周期钩子API](https://cn.vuejs.org/v2/guide/instance.html#实例生命周期钩子)

简单理解，生命周期钩子函数就是vue实例在某一个时间点会自动执行的函数。
<!-- more -->


```html
<div id="app">{{msg}}</div>

<script src="https://cdn.bootcss.com/vue/2.4.2/vue.js"></script>
<script>
  var vm = new Vue({
    el: '#app',
    data: {
      msg: 'Vue的生命周期'
    },
    beforeCreate: function() {
      console.group('------beforeCreate创建前状态------');
      console.log("el     : " + this.$el); //undefined
      console.log("data   : " + this.$data); //undefined
      console.log("msg: " + this.msg) //undefined
    },
    created: function() {
      console.group('------created创建完毕状态------');
      console.log("el     : " + this.$el); //undefined
      console.log("data   : " + this.$data); //已被初始化
      console.log("msg: " + this.msg); //已被初始化
    },
    beforeMount: function() {
      console.group('------beforeMount挂载前状态------');
      console.log(this.$el);// <div id="app">{{msg}}</div> 挂载前状态
    },
    mounted: function() {
      console.group('------mounted 挂载结束状态------');
      console.log(this.$el);// <div id="app">Vue的生命周期</div>   msg内容被挂载并渲染到页面
    },
      // 当data被修改之前
    beforeUpdate: function () {
      console.group('beforeUpdate 更新前状态===============》');
      console.log("el     : " + this.$el);
      console.log(this.$el);
      console.log("data   : " + this.$data);
      console.log("msg: " + this.msg);
    },
      // 触发beforeUpdate之后，虚拟DOM重新渲染并应用更新
      // 当data被修改之后
    updated: function () {
      console.group('updated 更新完成状态===============》');
      console.log("el     : " + this.$el);
      console.log(this.$el);
      console.log("data   : " + this.$data);
      console.log("msg: " + this.msg);
    },
      // 调用vm.$destroy() 销毁前
    beforeDestroy: function () {
      console.group('beforeDestroy 销毁前状态===============》');
      console.log("el     : " + this.$el);
      console.log(this.$el);
      console.log("data   : " + this.$data);
      console.log("msg: " + this.msg);
    },
       // 调用vm.$destroy() 销毁后
    destroyed: function () {
      console.group('destroyed 销毁完成状态===============》');
      console.log("el     : " + this.$el);
      console.log(this.$el);
      console.log("data   : " + this.$data);
      console.log("msg: " + this.msg)
    }
  })
</script>
```

## Demo

<p class="codepen" data-height="265" data-theme-id="light" data-default-tab="js,result" data-user="xugaoyi" data-slug-hash="GRJZWjb" style="height: 265px; box-sizing: border-box; display: flex; align-items: center; justify-content: center; border: 2px solid; margin: 1em 0; padding: 1em;" data-pen-title="生命周期钩子">
  <span>See the Pen <a href="https://codepen.io/xugaoyi/pen/GRJZWjb">
  生命周期钩子</a> by xugaoyi (<a href="https://codepen.io/xugaoyi">@xugaoyi</a>)
  on <a href="https://codepen.io">CodePen</a>.</span>
</p>
<script async src="https://static.codepen.io/assets/embed/ei.js"></script>



## 生命周期图示

![](https://cdn.staticaly.com/gh/xugaoyi/image_store/blog/20200204152241.png)