getGoogleCalendarEventID.js

(function() {
  function getGoogleCalendarEventID() {
    var elm = document.querySelector('div.ep[data-eid]');
    if (!elm) {
      return;
    }
    var eid = elm.getAttribute('data-eid');
    if (!eid) {
      return;
    }
    var ids = atob(eid).split(' ');
    var eventID = ids[0];
    var calendarID = ids[1];
    return {
      eventID: eventID,
      calendarID: calendarID,
    };
  }
  console.log(getGoogleCalendarEventID());
}())