实例生命周期钩子

实例生命周期钩子 API

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。

<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
    frontchen (<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