Function getTimingDataAsync

src/service/variable-source.js:74–106

(win, startEvent, endEvent)

 * @return {!Promise<ResolverReturnDef>}
 */
export function getTimingDataAsync(win, startEvent, endEvent) {
  // Fallback to load event if we don't know what to wait for
  const startWaitForEvent =
    NAV_TIMING_WAITFOR_EVENTS[startEvent] || WAITFOR_EVENTS_ENUM.LOAD;
  const endWaitForEvent = endEvent
    ? NAV_TIMING_WAITFOR_EVENTS[endEvent] || WAITFOR_EVENTS_ENUM.LOAD
    : startWaitForEvent;

  const waitForEvent = Math.max(startWaitForEvent, endWaitForEvent);

  // set wait for onload to be default
  let readyPromise;
  if (waitForEvent === WAITFOR_EVENTS_ENUM.VIEWER_FIRST_VISIBLE) {
    readyPromise = Promise.resolve();
  } else if (waitForEvent === WAITFOR_EVENTS_ENUM.DOCUMENT_COMPLETE) {
    readyPromise = whenDocumentComplete(win.document);
  } else if (waitForEvent === WAITFOR_EVENTS_ENUM.LOAD) {
    readyPromise = loadPromise(win);
  } else if (waitForEvent === WAITFOR_EVENTS_ENUM.LOAD_END) {
    // performance.timing.loadEventEnd returns 0 before the load event handler
    // has terminated, that's when the load event is completed.
    // To wait for the event handler to terminate, wait 1ms and defer to the
    // event loop.
    const timer = Services.timerFor(win);
    readyPromise = loadPromise(win).then(() => timer.promise(1));
  }

  devAssert(readyPromise, 'waitForEvent not supported ' + waitForEvent);

  return readyPromise.then(() => {
    return getTimingDataSync(win, startEvent, endEvent);
  });
}

/**
 * Returns navigation timing information based on the start and end events.