echarts 自定义tooltips

this.option.tooltip.formatter = function(a) {
           let list = []
           let listItem = ''
           for (var i = 0; i < a.length; i++) {
             list.push(
              '<div>&nbsp&nbsp' +
                 a[i].value[0] +
               '</div><i style="display: inline-block;width: 10px;height: 10px;background: ' +
                 a[i].color +
                 ';margin-right: 5px;border-radius: 50%;}"></i><span style="width:70px; display:inline-block;">' +
                 a[i].seriesName +
'&nbsp&nbsp'+

                 a[i].value[1] +'</span>'
             )
           }
           listItem = list.join('<br>')
           return '<div >' + listItem + '</div>'
         }