echarts 实现tooltip双栏效果

//option                    
tooltip: {
                        trigger: ‘axis‘,
                        axisPointer: {
                            label: {
                                show: true,
                                fontSize: 15
                            }
                        },
                        formatter: this.formatter
                    }, 

// formatter  function

formatter (params){
        let temp=[];
        let temp2=‘‘;
        let leftSide=‘‘;
        let rightSide=‘‘;
        for( let item of params){
            temp.push({
                seriesName:item.seriesName,
                value:item.value
            })
        }
        let arr=temp.sort(this.sortValue);
        let midValue=Math.ceil(arr.length/2);
        for(let [key,item] of arr.entries()){
            item.seriesName="测试数据";
            if(key< midValue&&midValue>4){
                if(isNaN(item.value)){
                    leftSide+=`${item.seriesName}: 无数据<br>`;
                }else{
                    leftSide+=`${item.seriesName}: ${item.value}<br>`;
                }
            }else{
                if(isNaN(item.value)){
                    rightSide+=`${item.seriesName}: 无数据<br>`;
                }else{
                    rightSide+=`${item.seriesName}: ${item.value}<br>`;
                }
            }
        }
        temp2=`<div class="my-flex">
            <div>${leftSide}</div>
            <div style="margin-left:20px;">${rightSide}</div>
            </div>`;
        return temp2;
    },