Calendar Blocking GScript

Code.gs

function sync() {
  // gcal IDs: email address if using default calendar
  const SOURCE_ID = "XXXXXX";
  const DEST_ID = "YYYYYY";

  // SETTINGS
  // how many days out to clone events
  const ADVANCE_DAYS = 5; // integer
  // title of cloned events
  const TITLE = "Busy 📵";

  const sourceCal = CalendarApp.getCalendarById(SOURCE_ID);
  const destCal = CalendarApp.getCalendarById(DEST_ID);

  const now = new Date();
  const enddate = new Date(now.getTime() + ADVANCE_DAYS * 24 * 60 * 60 * 1000);

  // events from source calendar, with all-day events removed
  const sourceEvents = sourceCal
    .getEvents(now, enddate)
    .filter(ev => !ev.isAllDayEvent());

  // event blocks already on work calendar
  const destEvents = dest.getEvents(now, enddate, { search: TITLE });

  // add blocks when one does not yet exist
  sourceEvents.forEach(event => {
    if (
      !destEvents.some(
        block =>
          event.getStartTime().getTime() === block.getStartTime().getTime() &&
          event.getStartTime().getTime() === block.getStartTime().getTime()
      )
    ) {
      destCal
        .createEvent(TITLE, event.getStartTime(), event.getEndTime())
        .removeAllReminders();
    }
  });

  // delete blocks when original event is removed
  destEvents.forEach(block => {
    if (
      !sourceEvents.some(
        event =>
          event.getStartTime().getTime() === block.getStartTime().getTime() &&
          event.getStartTime().getTime() === block.getStartTime().getTime()
      )
    ) {
      block.deleteEvent();
    }
  });
}