React Example: Virtualized Infinite Scrolling

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import React from 'react'
import ReactDOM from 'react-dom/client'
import './index.css'

// 3 TanStack Libraries!!!
import {
  columnSizingFeature,
  createColumnHelper,
  createSortedRowModel,
  rowSortingFeature,
  sortFns,
  tableFeatures,
  useTable,
} from '@tanstack/react-table'
import {
  QueryClient,
  QueryClientProvider,
  keepPreviousData,
  useInfiniteQuery,
} from '@tanstack/react-query'
import { useVirtualizer } from '@tanstack/react-virtual'
import { fetchData } from './makeData'
import type { Person, PersonApiResponse } from './makeData'
import type { OnChangeFn, SortingState } from '@tanstack/react-table'

const fetchSize = 50

const features = tableFeatures({
  columnSizingFeature,
  rowSortingFeature,
  sortedRowModel: createSortedRowModel(),
  sortFns,
})

const columnHelper = createColumnHelper<typeof features, Person>()

function App() {
  // we need a reference to the scrolling element for logic down below
  const tableContainerRef = React.useRef<HTMLDivElement>(null)

  const [sorting, setSorting] = React.useState<SortingState>([])

  const columns = React.useMemo(
    () =>
      columnHelper.columns([
        columnHelper.accessor('id', {
          header: 'ID',
          size: 60,
        }),
        columnHelper.accessor('firstName', {
          cell: (info) => info.getValue(),
        }),
        columnHelper.accessor((row) => row.lastName, {
          id: 'lastName',
          cell: (info) => info.getValue(),
          header: () => <span>Last Name</span>,
        }),
        columnHelper.accessor('age', {
          header: () => 'Age',
          size: 50,
        }),
        columnHelper.accessor('visits', {
          header: () => <span>Visits</span>,
          size: 50,
        }),
        columnHelper.accessor('status', {
          header: 'Status',
        }),
        columnHelper.accessor('progress', {
          header: 'Profile Progress',
          size: 80,
        }),
        columnHelper.accessor('createdAt', {
          header: 'Created At',
          cell: (info) => info.getValue<Date>().toLocaleString(),
          size: 200,
        }),
      ]),
    [],
  )

  // react-query has a useInfiniteQuery hook that is perfect for this use case
  const { data, fetchNextPage, isFetching, isLoading } =
    useInfiniteQuery<PersonApiResponse>({
      queryKey: [
        'people',
        sorting, // refetch when sorting changes
      ],
      queryFn: async ({ pageParam = 0 }) => {
        const start = (pageParam as number) * fetchSize
        const fetchedData = await fetchData(start, fetchSize, sorting) // pretend api call
        return fetchedData
      },
      initialPageParam: 0,
      getNextPageParam: (_lastGroup, groups) => groups.length,
      refetchOnWindowFocus: false,
      placeholderData: keepPreviousData,
    })

  // flatten the array of arrays from the useInfiniteQuery hook
  const flatData = React.useMemo(
    () => data?.pages.flatMap((page) => page.data) ?? [],
    [data],
  )
  const totalDBRowCount = data?.pages[0]?.meta?.totalRowCount ?? 0
  const totalFetched = flatData.length

  // called on scroll and possibly on mount to fetch more data as the user scrolls and reaches bottom of table
  const fetchMoreOnBottomReached = React.useCallback(
    (containerRefElement?: HTMLDivElement | null) => {
      if (containerRefElement) {
        const { scrollHeight, scrollTop, clientHeight } = containerRefElement
        // once the user has scrolled within 500px of the bottom of the table, fetch more data if we can
        if (
          scrollHeight - scrollTop - clientHeight < 500 &&
          !isFetching &&
          totalFetched < totalDBRowCount
        ) {
          fetchNextPage()
        }
      }
    },
    [fetchNextPage, isFetching, totalFetched, totalDBRowCount],
  )

  // a check on mount and after a fetch to see if the table is already scrolled to the bottom and immediately needs to fetch more data
  React.useEffect(() => {
    fetchMoreOnBottomReached(tableContainerRef.current)
  }, [fetchMoreOnBottomReached])

  const table = useTable(
    {
      features,
      data: flatData,
      columns,
      state: {
        sorting,
      },
      manualSorting: true,
      debugTable: true,
    },
    (state) => state, // default selector
  )

  // scroll to top of table when sorting changes
  const handleSortingChange: OnChangeFn<SortingState> = (updater) => {
    setSorting(updater)
    if (table.getRowModel().rows.length) {
      rowVirtualizer.scrollToIndex(0)
    }
  }

  // since this table option is derived from table row model state, we're using the table.setOptions utility
  table.setOptions((prev) => ({
    ...prev,
    onSortingChange: handleSortingChange,
  }))

  const { rows } = table.getRowModel()

  const rowVirtualizer = useVirtualizer({
    count: rows.length,
    estimateSize: () => 33, // estimate row height for accurate scrollbar dragging
    getScrollElement: () => tableContainerRef.current,
    // measure dynamic row height, except in firefox because it measures table border height incorrectly
    measureElement:
      typeof window !== 'undefined' &&
      navigator.userAgent.indexOf('Firefox') === -1
        ? (element) => element.getBoundingClientRect().height
        : undefined,
    overscan: 5,
  })

  if (isLoading) {
    return <>Loading...</>
  }

  return (
    <div className="app">
      {process.env.NODE_ENV === 'development' ? (
        <p>
          <strong>Notice:</strong> You are currently running React in
          development mode. Virtualized rendering performance will be slightly
          degraded until this application is built for production.
        </p>
      ) : null}
      ({flatData.length.toLocaleString()} of {totalDBRowCount.toLocaleString()}{' '}
      rows fetched)
      <div
        className="container"
        onScroll={(e) => fetchMoreOnBottomReached(e.currentTarget)}
        ref={tableContainerRef}
        style={{
          overflow: 'auto', // our scrollable table container
          position: 'relative', // needed for sticky header
          height: '600px', // should be a fixed height
        }}
      >
        {/* Even though we're still using sematic table tags, we must use CSS grid and flexbox for dynamic row heights */}
        <table style={{ display: 'grid' }}>
          <thead
            style={{
              display: 'grid',
              position: 'sticky',
              top: 0,
              zIndex: 1,
            }}
          >
            {table.getHeaderGroups().map((headerGroup) => (
              <tr
                key={headerGroup.id}
                style={{ display: 'flex', width: '100%' }}
              >
                {headerGroup.headers.map((header) => {
                  return (
                    <th
                      key={header.id}
                      style={{
                        display: 'flex',
                        width: header.getSize(),
                      }}
                    >
                      <div
                        className={
                          header.column.getCanSort() ? 'sortable-header' : ''
                        }
                        onClick={header.column.getToggleSortingHandler()}
                      >
                        <table.FlexRender header={header} />
                        {{
                          asc: ' 🔼',
                          desc: ' 🔽',
                        }[header.column.getIsSorted() as string] ?? null}
                      </div>
                    </th>
                  )
                })}
              </tr>
            ))}
          </thead>
          <tbody
            style={{
              display: 'grid',
              height: `${rowVirtualizer.getTotalSize()}px`, // tells scrollbar how big the table is
              position: 'relative', // needed for absolute positioning of rows
            }}
          >
            {rowVirtualizer.getVirtualItems().map((virtualRow) => {
              const row = rows[virtualRow.index]
              return (
                <tr
                  data-index={virtualRow.index} // needed for dynamic row height measurement
                  ref={(node) => rowVirtualizer.measureElement(node)} // measure dynamic row height
                  key={row.id}
                  style={{
                    display: 'flex',
                    position: 'absolute',
                    transform: `translateY(${virtualRow.start}px)`, // this should always be a `style` as it changes on scroll
                    width: '100%',
                  }}
                >
                  {row.getAllCells().map((cell) => {
                    return (
                      <td
                        key={cell.id}
                        style={{
                          display: 'flex',
                          width: cell.column.getSize(),
                        }}
                      >
                        <table.FlexRender cell={cell} />
                      </td>
                    )
                  })}
                </tr>
              )
            })}
          </tbody>
        </table>
      </div>
      {isFetching && <div>Fetching More...</div>}
    </div>
  )
}

const rootElement = document.getElementById('root')

if (!rootElement) throw new Error('Failed to find the root element')

const queryClient = new QueryClient()

ReactDOM.createRoot(rootElement).render(
  <React.StrictMode>
    <QueryClientProvider client={queryClient}>
      <App />
    </QueryClientProvider>
  </React.StrictMode>,
)