props傳值遇Cannot read property getAttribute of undefined異常

今有一個echarts 圖標的子組件使用watch 監聽接受父組件傳入的data，而在父組件頁面再次根據日期篩選數據，重新傳入子組件進行圖表重繪時老實會提示報錯

vue.runtime.esm.js?6e6d:619 [Vue warn]: Error in callback for watcher "chartData": "TypeError: Cannot read property 'getAttribute' of undefined"

found in

原來是異步加載數據切換的鍋，watch 中是一個異步函數，再監聽到值變化後，真正的值其實並未返回

  watch: {
    chartData(val) {
      if (val) {
        this.chartParentShow = true
        this.$nextTick(() => {
          this.drawLine(val)
        })
      } else {
        this.chartParentShow = false
      }
    }
  },