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

To scroll a virtualized list using recursion until a specific row has entered the viewport, we can use the following steps:

  1. Get the total number of rows in the virtualized list
  2. Calculate the height of each row in the list
  3. Calculate the top position of the desired row
  4. Use Cypress's scrollTo() command to scroll the list to the desired top position
  5. Wait for the list to finish rendering after each scroll
  6. Check if the desired row is now visible in the viewport
  7. If the row is visible, return it. If not, repeat the process with a new scroll position until it is visible.

Here's an example implementation:

index.tsx
// Recursive function to scroll the virtualized list
function scrollListUntilRowVisible(rowIndex, listSelector, rowSelector, rowHeight) {
  // Get the total number of rows in the list
  const totalRows = Cypress.$(listSelector).find(rowSelector).length;

  // Calculate the top offset of the desired row
  const rowTopOffset = rowIndex * rowHeight;

  // Scroll the list to the desired row
  cy.get(listSelector)
    .scrollTo(0, rowTopOffset)
    .wait(500) // Wait for the list to render

  // Check if the desired row is in the viewport
  cy.get(listSelector)
    .find(rowSelector)
    .eq(rowIndex)
    .then((row) => {
      const rowRect = row[0].getBoundingClientRect();
      const listRect = Cypress.$(listSelector)[0].getBoundingClientRect();

      if (rowRect.top < listRect.top || rowRect.bottom > listRect.bottom) {
        // If the row is not visible, recursively scroll with a new position
        return scrollListUntilRowVisible(rowIndex, listSelector, rowSelector, rowHeight);
      }

      // If the row is visible, return it
      return row;
    });
}
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To use this function, simply call it with the index of the desired row, selectors for the virtualized list and each row, and the height of each row:

index.tsx
scrollListUntilRowVisible(42, '#my-virtualized-list', '.row', 50).then((row) => {
  // Do something with the visible row
});
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Note: In the example implementation, I've used a fixed wait time of 500ms after each scroll to allow the list to render. Depending on the size of the list and the speed of the machine running the tests, you may need to adjust this time to ensure the list is fully rendered before checking for a visible row.

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