Vue+el-table realizes merging cells

<el-table :header-cell-style="{background:'#eef1f6',color:'#606266'}" :data="merchantList" border :span-method="arraySpanMethod">
          <el-table-column align="center" prop="provinceName" label="Province"> </el-table-column>
          <el-table-column align="center" label="Agent Name">
            <template scope="scope">
              <span>{{scope.row.parentMerchantName == scope.row.merchantName ? '---' : scope.row.parentMerchantName}}</span>
            </template>
          </el-table-column>
          <el-table-column align="center" prop="cityName" label="市"> </el-table-column>
          <el-table-column align="center" prop="countryName" label="区"> </el-table-column>
          <el-table-column align="center" prop="merchantName" label="店铺"> </el-table-column>
</el-table>

//Merge cells arraySpanMethod ({ row, column, rowIndex, columnIndex }) {
      if (columnIndex === 0) {//Merge method for the first column, province const _row_1 = this.provinceArr[rowIndex];
        const _col_1 = _row_1 > 0 ? 1 : 0; //If it is merged, _row=0, then this column needs to be cancelled return {
          rowspan: _row_1,
          colspan: _col_1
        }
      } 
    },
    // Initialize merageInit () {
      this.provinceArr = []
      this.provincePos = 0
    },
    //Method of merging arrays merge() {
      this.merageInit()
      for (var i = 0; i < this.merchantList.length; i++) {
        if (i === 0) {
          //The first line must exist this.provinceArr.push(1)
          this.provincePos = 0
        } else {
          // Determine whether the current element is the same as the previous element this.provincePos is the serial number of the provinceArr content //province if (this.merchantList[i].provinceName === this.merchantList[i - 1].provinceName) {
            this.provinceArr[this.provincePos] += 1
            this.provinceArr.push(0)
          } else {
            this.provinceArr.push(1)
            this.provincePos = i
          }
        }
      }
    },