vue+el-table实现合并单元格

<el-table :header-cell-style="{background:'#eef1f6',color:'#606266'}" :data="merchantList" border :span-method="arraySpanMethod">
          <el-table-column align="center" prop="provinceName" label="省份"> </el-table-column>
          <el-table-column align="center" label="代理商名称">
            <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="门店"> </el-table-column>
</el-table>

//合并单元格
arraySpanMethod ({ row, column, rowIndex, columnIndex }) {
      if (columnIndex === 0) {//第一列的合并方法,省
        const _row_1 = this.provinceArr[rowIndex];
        const _col_1 = _row_1 > 0 ? 1 : 0; //如果被合并了_row=0则它这个列需要取消
        return {
          rowspan: _row_1,
          colspan: _col_1
        }
      } 
    },
    //初始化
    merageInit () {
      this.provinceArr = []
      this.provincePos = 0
    },
    //要合并的数组的方法
    merage () {
      this.merageInit()
      for (var i = 0; i < this.merchantList.length; i++) {
        if (i === 0) {
          //第一行必须存在
          this.provinceArr.push(1)
          this.provincePos = 0
        } else {
          // 判断当前元素与上一个元素是否相同 this.provincePos是provinceArr内容的序号
          //省
          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
          }
        }
      }
    },