实例生命周期钩子

实例生命周期钩子 API (opens new window)

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

See the Pen 生命周期钩子 by xugaoyi (@xugaoyi) on CodePen.

生命周期图示