elementui的table合并列，三个一组

 <el-table :span-method="objectSpanMethod" :cell-style="iCellStyle" :data="tableData" height="63vh" border style="width: 100%; margin-top: 6px"><el-table-column type="index" label="序号" width="50" align="center"></el-table-column><el-table-column prop="vocs" label="VOCs组分" align="center"></el-table-column><el-table-column label="源成分谱" align="center"><template slot-scope="{row}"><span v-if="row.type==1">化工</span><span v-if="row.type==2">制造业</span><span v-if="row.type==3">交通运输</span></template></el-table-column><el-table-column prop="value" label="成分浓度(ug/m3)" align="center"></el-table-column><el-table-column prop="rate" label="成分浓度贡献率" align="center"></el-table-column></el-table>

this.tableData=[{"type": "1","value": 8.008,"rate": 28.241932639746075,"vocs": "乙烷"},{"type": "2","value": 7.862,"rate": 27.727032269441022,"vocs": "乙烷"},{"type": "3","value": 12.485,"rate": 44.03103509081291,"vocs": "乙烷"},{"type": "1","value": 11.184,"rate": 39.46226315232349,"vocs": "乙烯"},{"type": "2","value": 12.289,"rate": 43.361208143678766,"vocs": "乙烯"},{"type": "3","value": 4.868,"rate": 17.176528703997743,"vocs": "乙烯"},{"type": "1","value": 7.467,"rate": 30.569884549250798,"vocs": "丙烷"},{"type": "2","value": 8.686,"rate": 35.56046835339393,"vocs": "丙烷"},{"type": "3","value": 8.273,"rate": 33.869647097355276,"vocs": "丙烷"},{"type": "1","value": 2.832,"rate": 11.786739917592708,"vocs": "丙烯"},{"type": "2","value": 8.472,"rate": 35.260332126357845,"vocs": "丙烯"},{"type": "3","value": 12.723,"rate": 52.95292795604944,"vocs": "丙烯"},{"type": "1","value": 8.091,"rate": 41.29957633607268,"vocs": "异丁烷"},{"type": "2","value": 6.747,"rate": 34.43928334439283,"vocs": "异丁烷"},{"type": "3","value": 4.753,"rate": 24.26114031953448,"vocs": "异丁烷"},{"type": "1","value": 1.93,"rate": 11.623005118940078,"vocs": "乙炔"},{"type": "2","value": 5.598,"rate": 33.71273712737127,"vocs": "乙炔"},{"type": "3","value": 9.077,"rate": 54.66425775368865,"vocs": "乙炔"},{"type": "1","value": 2.265,"rate": 13.758124278685537,"vocs": "正丁烷"},{"type": "2","value": 6.344,"rate": 38.53489643442872,"vocs": "正丁烷"},{"type": "3","value": 7.854,"rate": 47.70697928688574,"vocs": "正丁烷"},{"type": "1","value": 4.244,"rate": 60.99453866053464,"vocs": "反-2-丁烯"},{"type": "2","value": 1.362,"rate": 19.5745903995401,"vocs": "反-2-丁烯"},{"type": "3","value": 1.352,"rate": 19.430870939925267,"vocs": "反-2-丁烯"},{"type": "1","value": 0.236,"rate": 3.935957304869913,"vocs": "1-丁烯"},{"type": "2","value": 0.634,"rate": 10.57371581054036,"vocs": "1-丁烯"},{"type": "3","value": 5.126,"rate": 85.49032688458973,"vocs": "1-丁烯"},{"type": "1","value": 1.772,"rate": 37.32097725358046,"vocs": "顺-2-丁烯"},{"type": "2","value": 2.192,"rate": 46.16680707666386,"vocs": "顺-2-丁烯"},{"type": "3","value": 0.784,"rate": 16.512215669755687,"vocs": "顺-2-丁烯"}
]this.flagValue = "";this.flagArr = [];this.indexAllArr = [];this.intervalArr = [];let indexArr = [];this.tableData.forEach((item, index) => {if (this.flagValue != item.vocs) {if (!this.flagArr.includes(item.vocs)) {this.flagArr.push(item.vocs);this.indexAllArr.push(index);indexArr.push(index);} else {this.indexAllArr.push("-");}}});// 计算每一种类型都有多少个indexArr.forEach((ele, eleIndex) => {var indexNum = "";if (indexArr[eleIndex] != indexArr[indexArr.length - 1]) {indexNum = indexArr[eleIndex + 1] - ele;} else {indexNum = this.tableData.length - indexArr[eleIndex];}this.intervalArr.push(indexNum);});this.indexAllArr.forEach((item, index) => {if (!isNaN(Number(item)) && typeof Number(item) === "number") {} else {this.intervalArr.splice(index, 0, "-");}});

 // 合并列objectSpanMethod({ row, column, rowIndex, columnIndex }) {if (columnIndex === 1) {const _row = this.indexAllArr[rowIndex];const rowspanVal = this.intervalArr[rowIndex];if (rowIndex == _row) {return {rowspan: rowspanVal,colspan: 1,};}else{return {rowspan: 0,colspan: 0,};}}},iCellStyle: function ({ row, column, rowIndex, columnIndex }) {return "height:44px !import";},