The echots in Vue reports an error. After obtaining the DOM element, the chart can be displayed. The console still reports an error

 <div v-if="grade<3" ref="gradeChart" style="height: 220px;width: 300px;margin:0 auto;">




  mounted() {
      this.$nextTick(() => {
				setTimeout(()=>{
					let map1=this.initEchartMap(this.gjfsx);
					console.log(this.$refs.gradeChart,"ddkiiok")
					},50)
      })

 

  The solution is to change V-IF to v-show, and the console will not report an error

 <div v-show="grade<3" ref="gradeChart" style="height: 220px;width: 300px;margin:0 auto;">