V8 header groups & header rowSpan

[LoicUV]

Hi folks 👋

I'm having a bit of trouble understanding how rowSpan works for headers, especially when working with header groups.

The column group demo renders header groups by looping over table.getHeaderGroups(), creating a <tr> for each group, looping over group headers and returning null inside <th> when the header isPlaceholder value is true, which results in empty header cells depending on the structure

Ideally it should look like (at least in my use case)

To achieve that I'd have to

• loop over the groups
• identify if a group is a placeholder and contains subHeaders and how deep until reaching a non-placeholder subHeader
• render a <th> with a value of the depth found
• in subsequent groups, don't render a <th> for the headers that are already "covered" by the rowSpan of the parent

Does someone know how to achieve this in a simpler way ?

Couldn't it possible to manually declare a rowSpan in columnDef, which would be taken into account when building the groups ?
I found here that header supports rowSpan, but I'm not sure how it's calculated, it always seem to be 0.

What do you think ?

Edit :
I managed to make it work by adding a custom rowSpan in column meta in combination with the following render logic :

        <thead>
          {table.getHeaderGroups().map((headerGroup) => (
            <tr key={headerGroup.id}>
              {headerGroup.headers.map((header) => {
                const rowSpan = header.column.columnDef.meta?.rowSpan;

                if (
                  !header.isPlaceholder &&
                  rowSpan !== undefined &&
                  header.id === header.column.id
                ) {
                  return null;
                }

                return (
                  <th
                    key={header.id}
                    colSpan={header.colSpan}
                    rowSpan={rowSpan}
                  >
                    {flexRender(
                      header.column.columnDef.header,
                      header.getContext()
                    )}
                  </th>
                );
              })}
            </tr>
          ))}
        </thead>

But it feels kinda wrong and displays some header twice if you don't supply a rowSpan when needed.
Here's a codesandbox if you want to tinker with it.

[Hristy-A]

@LoicUV Thanks for the good idea via meta!

I experimented a bit based on your solution and got it to work automatically, but didn't test on large nesting:

        <thead>
          {table.getHeaderGroups().map((headerGroup) => (
            <tr key={headerGroup.id}>
              {headerGroup.headers.map((header) => {
                const columnRelativeDepth = header.depth - header.column.depth;

                if (
                  !header.isPlaceholder &&
                  columnRelativeDepth > 1 &&
                  header.id === header.column.id
                ) {
                  return null;
                }

                let rowSpan = 1;
                if (header.isPlaceholder) {
                  const leafs = header.getLeafHeaders();
                  rowSpan = leafs[leafs.length - 1].depth - header.depth;
                }

                return (
                  <th
                    key={header.id}
                    colSpan={header.colSpan}
                    rowSpan={rowSpan}
                  >
                    {flexRender(
                      header.column.columnDef.header,
                      header.getContext(),
                    )}
                  </th>
                );
              })}
            </tr>
          ))}
        </thead>

My logic is that columns have the smallest depth, relative to the nested columns. And if the column depth is more than 1 greater than the column depth, it means that there is a placeholder and we don't display this header.
Link to sandbox

The rowSpan is calculated by the reverse logic - relative to the deepest leaf :)

P.S. I couldn't figure out how to use the built-in rowSpan either. Do you have any new information about it?

[TofuTseng]

really save my day!

[IzraNovan]

can you give me a source code? i can't get to that sandbox link

[TsengTofu]

@IzraNovan
Here is the link

[anton-paskanny]

I've been playing around with the initial solution to adapt it to the 3rd level of nesting. Here is the link to the sandbox. I see that some header cells are duplicated. Any suggestions why?

[anton-paskanny]

Updated: I've just added a check to determine if the header had been already rendered and it seems to be working correctly.

[leookun]

@Hristy-A thanks! I use the following code to implement this interesting feature in vue

import { FlexRender } from "@tanstack/vue-table";
export const Thead = ({ table }) => {
    return <thead>
        {table.getHeaderGroups().map((headerGroup) => (
            <tr key={headerGroup.id}>
                {headerGroup.headers.map((header) => {
                    const columnRelativeDepth = header.depth - header.column.depth;

                    if (
                        columnRelativeDepth > 1
                    ) {

                        return null;
                    }

                    let rowSpan = 1;
                    if (header.isPlaceholder) {
                        const leafs = header.getLeafHeaders();
                        rowSpan = leafs[leafs.length - 1].depth - header.depth;
                    }

                    return (
                        <th
                            data-columnRelativeDepth={columnRelativeDepth}
                            key={header.id}
                            colspan={header.colSpan}
                            rowspan={rowSpan}
                        >
                            <FlexRender
                                render={header.column.columnDef.header}
                                props={header.getContext()}
                            />

                        </th>
                    );
                })}
            </tr>
        ))}
    </thead>
}

[shreejeshballal]

Could you please share the column definition of the table?

[Yuki-Izuna]

hello.
I was also able to do it by imitating @leookun implementation !

import * as React from "react";
import ReactDOM from "react-dom/client";


import {
  ColumnDef,
  createColumnHelper,
  flexRender,
  getCoreRowModel,
  useReactTable,
} from "@tanstack/react-table";

declare module "@tanstack/table-core" {
  // @ts-expect-error
  interface ColumnMeta<TData extends RowData, TValue> {
    rowSpan?: number;
  }
}

type Person = {
  test?: string,
  firstName: string;
  lastName: string;
  age: number;
  visits: number;
  status: string;
  progress: number;
};

const defaultData: Person[] = [
  {
    test: "aaa",
    firstName: "tanner",
    lastName: "linsley",
    age: 24,
    visits: 100,
    status: "In Relationship",
    progress: 50,
  },
  {
    test: "bbb",
    firstName: "tandy",
    lastName: "miller",
    age: 40,
    visits: 40,
    status: "Single",
    progress: 80,
  },
  {
    test: "ccc",
    firstName: "joe",
    lastName: "dirte",
    age: 45,
    visits: 20,
    status: "Complicated",
    progress: 10,
  },
];

const columnHelper = createColumnHelper<Person>();

const columns = [
  columnHelper.accessor("test", {
    cell: (info) => info.getValue(),

    meta: {
      rowSpan: 3,
    },
  }),
  columnHelper.group({
    id: "hello",
    header: () => <span>Hello</span>,
    columns: [
      columnHelper.accessor("firstName", {
        cell: (info) => info.getValue(),

        meta: {
          rowSpan: 2,
        },
      }),
      columnHelper.accessor((row) => row.lastName, {
        id: "lastName",
        cell: (info) => info.getValue(),
        header: () => <span>Last Name</span>,
        meta: {
          rowSpan: 2,
        },
      }),
    ],
  }),
  columnHelper.group({
    header: "Info",
    columns: [
      columnHelper.accessor("age", {
        header: () => "Age",
        meta: {
          rowSpan: 2,
        },
      }),
      columnHelper.group({
        header: "More Info",
        columns: [
          columnHelper.accessor("visits", {
            header: () => <span>Visits</span>,
          }),
          columnHelper.accessor("status", {
            header: "Status",
          }),
          columnHelper.accessor("progress", {
            header: "Profile Progress",
          }),
        ],
      }),
    ],
  }),
];

export default function FlexibleHeaderTable() {
  const [data, setData] = React.useState(() => [...defaultData]);
  const rerender = React.useReducer(() => ({}), {})[1];

  const table = useReactTable({
    data,
    columns,
    getCoreRowModel: getCoreRowModel(),
  });

  return (
    <div className="p-2">
      <table style={{ borderCollapse: 'collapse', width: '100%', border: '1px solid #e5e7eb' }}>
        <thead>
          {table.getHeaderGroups().map((headerGroup) => (
            <tr key={headerGroup.id}                   >
              {headerGroup.headers.map((header) => {

                const columnRelativeDepth = header.depth - header.column.depth;
                if (
                  columnRelativeDepth > 1
              ) {

                  return null;
              }

                let rowSpan = 1;
                if (header.isPlaceholder) {
                    const leafs = header.getLeafHeaders();
                    rowSpan = leafs[leafs.length - 1].depth - header.depth;
                }



                return (
                  <th
                    key={header.id}
                    colSpan={header.colSpan}
                    rowSpan={rowSpan}
                    style={{
                      padding: '12px',
                      textAlign: 'left',
                      fontSize: '0.75rem',
                      fontWeight: 'medium',
                      color: '#6b7280',
                      textTransform: 'uppercase',
                      letterSpacing: '0.05em',
                      backgroundColor: '#f9fafb',
                      border: '1px solid #e5e7eb',
                    }}
                  >
                    {flexRender(
                      header.column.columnDef.header,
                      header.getContext()
                    )}
                  </th>
                );
              })}
            </tr>
          ))}
        </thead>
        <tbody>
          {table.getRowModel().rows.map((row) => (
            <tr key={row.id}>
              {row.getVisibleCells().map((cell) => (
                <td key={cell.id}                   style={{
                  padding: '12px',
                  whiteSpace: 'nowrap',
                  fontSize: '0.875rem',
                  color: '#6b7280',
                  border: '1px solid #e5e7eb',
                }}>
                  {flexRender(cell.column.columnDef.cell, cell.getContext())}
                </td>
              ))}
            </tr>
          ))}
        </tbody>
      </table>
    </div>
  );
}

[shreejeshballal]

Thank you boss!

[jacksonkasi1]

Repo: https://github.com/jacksonkasi1/FlexiSheet

Demo: https://flexisheet.vercel.app/

Blog: https://dev.to/jacksonkasi/building-a-google-sheets-like-table-component-with-tanstack-table-zod-and-shadcnui-1ped