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
      }
    },