vue监听浏览器窗口的变化，随着窗口变化调整里面table的宽高

1.在data中设置：

  tableHeight:"500",
  screenHeight:window.innerHeight,

2.在mounted中设置：

   mounted() {
       const that = this
       window.onresize =()  =>{
         return (()=>{
           window.screenHeight = window.innerHeight
           this.screenHeight = window.screenHeight;
         })()
       }
     },

3.在watch中监听：

   watch:{
       screenHeight(val){
         this.screenHeight = val
         this.tableHeight = this.screenHeight - 250
       }
     },