elementui组件table表，同时合并列合并行的解决办法

项目需要实现每三行合并两行，然后每三行合并三列，下图这种效果：

代码：

el-table
      :data="tableData"
      :span-method="arraySpanMethod"
      border
      style="width: 100%">
      <el-table-column
        prop="id"
        label="ID"
        width="180">
      </el-table-column>
      <el-table-column
        prop="name"
        label="姓名">
      </el-table-column>
      <el-table-column
        prop="amount1"
        sortable
        label="数值 1">
      </el-table-column>
      <el-table-column
        prop="amount2"
        sortable
        label="数值 2">
      </el-table-column>
      <el-table-column
        prop="amount3"
        sortable
        label="数值 3">
      </el-table-column>
    </el-table>

vue部分：

var Main = {
    data() {
      return {
        tableData: [{
          id: '12987122',
          name: '王小虎',
          amount1: '234',
          amount2: '3.2',
          amount3: 10
        }, {
          id: '12987123',
          name: '王小虎',
          amount1: '165',
          amount2: '4.43',
          amount3: 12
        }, {
          id: '12987124',
          name: '王小虎',
          amount1: '324',
          amount2: '1.9',
          amount3: 9
        }, {
          id: '12987125',
          name: '王小虎',
          amount1: '621',
          amount2: '2.2',
          amount3: 17
        }, {
          id: '12987126',
          name: '王小虎',
          amount1: '539',
          amount2: '4.1',
          amount3: 15
        }, {
          id: '12987126',
          name: '王小虎',
          amount1: '666',
          amount2: '4.1',
          amount3: 15
        }, {
          id: '12987126',
          name: '王小虎',
          amount1: '777',
          amount2: '4.1',
          amount3: 15
        }, {
          id: '12987126',
          name: '王小虎',
          amount1: '888',
          amount2: '4.1',
          amount3: 15
        }, {
          id: '12987126',
          name: '王小虎',
          amount1: '999',
          amount2: '4.1',
          amount3: 15
        }]
      };
    },
    methods: {
      arraySpanMethod({ row, column, rowIndex, columnIndex }) {
        
        if(columnIndex === 0) {
          if ((rowIndex+1) % 3 === 1) {
            return {
              rowspan: 2,
              colspan: 1
            };
          }else if ((rowIndex+1) % 3 === 0 ) {
            return [1, 3];
          }
        }
      },

      objectSpanMethod({ row, column, rowIndex, columnIndex }) {
        
      }
    }
  };
var Ctor = Vue.extend(Main)
new Ctor().$mount('#app')