function maybeUpdateEndField(start_date_field: HTMLInputElement) {
  let end_date_field: HTMLInputElement | null | undefined = start_date_field
    ?.closest(".form-row")
    ?.querySelector(".field-end .vDateField");
  if (end_date_field && !end_date_field.value) {
    end_date_field.value = start_date_field.value;
  }
}

function setupListeners(element: ParentNode) {
  for (let start_date_field of element.querySelectorAll(
    "#meeting_times-group .field-start .vDateField",
  ) as NodeListOf<HTMLInputElement>) {
    start_date_field.addEventListener("change", () => {
      maybeUpdateEndField(start_date_field);
    });
    // element is focused after selecting a date using Django's DateTimeShortcuts
    start_date_field.addEventListener("focus", () => {
      maybeUpdateEndField(start_date_field);
    });
  }
}

$(() => setupListeners(document));
$(document).on("formset:added", (event) => setupListeners(event.target));