The el-table header merges the first four columns into one cell

 <el-table :data="tableData1" fit size="mini"   ref="tableList"   :header-cell- 
    style="cells"   border  :height="tableHeight" style="width: 100%;"   > 
 <el-table-column  prop="categoryName" label="" fixed  align="left"  width="30" show- 
      overflow-tooltip>  </el-table-column>
 <el-table-column  prop="categoryId" label="" fixed align="left"  width="30" show-overflow- 
   tooltip> </el-table-column>
 <el-table-column  prop="subCategoryName" label="" fixed  align="left"  width="35" show-overflow-tooltip> </el-table-column>
 <el-table-column  prop="subCategoryId" label="类别" fixed align="left"  width="30" show- 
     overflow-tooltip> </el-table-column>
 <el-table-column  prop="name" label="名称" fixed align="center" width="180" > </el- 
     table-column>
 <el-table-column prop="unit" label="单位"  fixed align="center" width="80"></el-table- 
   column>

As shown in the figure, the first four columns are merged into one cell, and only the category is displayed. Then use the attribute: header-cell-style, which has four parameters, corresponding to the row, column, row index, and column index, so directly Just write it in the cells method:

  // 头部样式   前四列合并
  cells({row, column, rowIndex, columnIndex}) {
      console.log(row,column,rowIndex,columnIndex)
      if (row[0].level==1) {
          row[0].colSpan = 0;
          row[1].colSpan = 0;
          row[2].colSpan = 0;
          row[3].colSpan = 4;
          if (columnIndex === 0 ||columnIndex===1 ||columnIndex===2 ) {
                  return { display: "none" };
             }
         }
       //改变当前行样式
       return "font-size:14px;color:#fff;background:#4F81BD;";
  },

In this way, the first four columns are merged into one cell.