方法一：

First-step : 定义变量

data(){
    return{
          formLabelWidth : '123px'
    }
},

Second-step:   根据生命周期 在mounted 中绑定 窗口变化

 mounted(){
              const that = this
              window.onresize = () => {
                  return (() => {
                    window.screenWidth = document.body.clientWidth
                    that.screenWidth = window.screenWidth
                 })()
              }
 },

Third-step:   绑定监听 watch

 watch: {
              screenWidth (val) {
                        if (!this.timer) {
                            this.screenWidth = val
                            this.timer = true
                            let that = this
                            setTimeout(function () {
                                // that.screenWidth = that.$store.state.canvasWidth
                                console.log(that.screenWidth)
                                // that.init()
                                that.timer = false
                            }, 400)
                        }
              }
  },

方法二：在vue.2x里面时候，mounted 里面可以直接挂载 window.onresize事件。全局监听

 mounted(){

              window.onresize = () => {
                  return (() => {
                      this.handleLableWidth();
                 })()
              }
              this.handleLableWidth();

},

完全可以做到检测窗口变化