vuejs生命周期函数(什么是vue的生命周期)

<div id="app">{
  
  {a}}</div>

<script>
var myVue = new Vue({
  el: '#app',
  data: {
    a: 'Vue.js'
  },
  beforeCreate: function() {
    console.log('创建前')
    console.log(this.a)
    console.log(this.$el)
  },
  created: function() {
    console.log('创建之后')
    console.log(this.a)
    console.log(this.$el)
  },
  beforeMount: function() {
    console.log('mount之前')
    console.log(this.a)
    console.log(this.$el)
  },
  mounted: function() {
    console.log('mount之后')
    console.log(this.a)
    console.log(this.$el)
  },
  beforeUpdate: function() {
    console.log('更新前')
    console.log(this.a)
    console.log(this.$el)
  },
  updated: function() {
    console.log('更新完成')
    console.log(this.a)
    console.log(this.$el)
  },
  beforeDestroy: function() {
    console.log('销毁前')
    console.log(this.a)
    console.log(this.$el)
    console.log(this.$el)
  },
  destroyed: function() {
    console.log('已销毁')
    console.log(this.a)
    console.log(this.$el)
  }
})
</script>

<div id=app>{
  
  {a}}
<button v-on:click="change">change</button>
</div>


methods:{
    change(){
        this.a = 'change vue'
    }
}