recursively scroll a virtualized list until a row has entered the viewport in javascript

To recursively scroll a virtualized list until a row has entered the viewport, you need to make use of the scrollToIndex method provided by the virtualized list library. The scrollToIndex function accepts an index argument and an optional align argument, that determines how the list should be scrolled to the desired row.

One approach to recursively scroll the list to the desired row is to use a recursive function that repeatedly calls scrollToIndex with an incremented index argument until the row is in the viewport. Here's an example of how you can implement this:

index.tsx
function scrollToListItem(list, rowIndex) {
  const { startIndex, stopIndex } = list.state;
  if (rowIndex >= startIndex && rowIndex <= stopIndex) {
    // the item is already visible in the viewport
    return;
  }

  // calculate the index to scroll to
  const index =
    rowIndex < startIndex
      ? Math.max(rowIndex - 10, 0) // scroll back 10 items
      : Math.min(rowIndex + 10, list.props.itemCount - 1); // scroll forward 10 items

  // scroll to the index using the scrollToIndex method
  list.scrollToIndex({ index, align: 'start' });

  // wait for the list to render the scrolled items
  requestAnimationFrame(() => {
    // recursively scroll the list to the desired row
    scrollToListItem(list, rowIndex);
  });
}
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In this example, the scrollToListItem function takes a virtualized list component and a rowIndex parameter as arguments. It first checks if the item is already visible in the viewport by comparing the row index with the startIndex and stopIndex values of the list's state. If the item is not visible, the function calculates the index to scroll to by adding or subtracting 10 items from the current row index. It then calls the scrollToIndex function with the calculated index and the start alignment.

After scrolling to the desired index, the function waits for the list to render the scrolled items using the requestAnimationFrame method. Once the items are rendered, the function calls itself recursively with the original rowIndex parameter to check if the row is now visible in the viewport. This process is repeated until the row is visible, after which the function returns.