生命周期（vue的钩子函数）

生命周期图示

• 创建前，创建后，挂载前，挂载后，更新前，更新后，销毁前，销毁后
  

beforeCreate:function(){
      console.log('1-beforeCreate 组件还未被创建');
},
created:function(){
      console.log('2-created 组件已被创建');
},
beforeMount:function(){
       console.log('3-beforeMount 组件已创建但还未挂载到DOM节点上');
},
mounted:function(){
       console.log('4-mounted 组件已挂载到DOM节点上');
},
beforeUpdate:function(){
       console.log('5-beforeUpdate 数据更新前');
},
updated:function(){
       console.log('6-updated 被更新后');
},
activated:function(){
        console.log('7-activated');
},
deactivated:function(){
       console.log('8-deactivated');
},
beforeDestroy:function(){
       console.log('9-beforeDestroy 组件即将被销毁');
},
destroyed:function(){
       console.log('10-destroyed 组件已经被销毁')
}

<button onclick='app.$destroy()'>销毁</button>

$el、$data

created和mounted

• beforeCreate:el和data并未初始化

• created:完成了data数据的初始化，el没有

• beforeMount: 完成了el和data初始化

• mounted: 完成挂载

    beforeCreate:function(){
    	console.log('1-beforeCreate 组件还未被创建');
    	console.log("%c%s", "color:red" , "el     : " + this.$el); //undefined
    	console.log("%c%s", "color:red","data   : " + this.$data); //undefined
    	console.log("%c%s", "color:red","message: " + this.message)//undefined
    }
  

	created:function(){
    	console.log('2-created 组件已被创建');
    	console.log("%c%s", "color:red","el     : " + this.$el); //undefined
   	 	console.log("%c%s", "color:red","data   : " + this.$data); //已被初始化
    	console.log("%c%s", "color:red","message: " + this.message); //已被初始化
	}

	beforeMount:function(){
    	console.log('3-beforeMount 组件已创建但还未挂载到DOM节点上');
    	console.log("%c%s", "color:red","el     : " + (this.$el)); //undefined
    	console.log(this.$el);
    	console.log("%c%s", "color:red","data   : " + this.$data); //已被初始化
    	console.log("%c%s", "color:red","message: " + this.message); //已被初始化
	}

• beforeMount 在.vue文件中el还没被创建

            beforeMount: function () {
                console.log('beforeMount 挂载前状态===============》');
                console.log("%c%s", "color:red","el     : " + (this.$el));//已被初始化
                console.log(this.$el);
                console.log("%c%s", "color:red","data   : " + this.$data);//已被初始化
                console.log("%c%s", "color:red","message: " + this.message);//已被初始化
            }

• beforeMount在html文件中el已被初始化

	mounted:function(){
    	console.log('4-mounted 组件已挂载到DOM节点上');
   	 	console.log("%c%s", "color:red","el     : " + this.$el); //已被初始化
    	console.log(this.$el);
    	console.log("%c%s", "color:red","data   : " + this.$data); //已被初始化
    	console.log("%c%s", "color:red","message: " + this.message); //已被初始化
	}