Function wrapFn

packages/zone.js/lib/common/utils.ts:137–195

(this: unknown, event: Event)

const enableBeforeunloadSymbol = zoneSymbol('enable_beforeunload');

const wrapFn = function (this: unknown, event: Event) {
  // https://github.com/angular/zone.js/issues/911, in IE, sometimes
  // event will be undefined, so we need to use window.event
  event = event || _global.event;
  if (!event) {
    return;
  }
  let eventNameSymbol = zoneSymbolEventNames[event.type];
  if (!eventNameSymbol) {
    eventNameSymbol = zoneSymbolEventNames[event.type] = zoneSymbol('ON_PROPERTY' + event.type);
  }
  const target = this || event.target || _global;
  const listener = target[eventNameSymbol];
  let result;
  if (isBrowser && target === internalWindow && event.type === 'error') {
    // window.onerror have different signature
    // https://developer.mozilla.org/en-US/docs/Web/API/GlobalEventHandlers/onerror#window.onerror
    // and onerror callback will prevent default when callback return true
    const errorEvent: ErrorEvent = event as any;
    result =
      listener &&
      listener.call(
        this,
        errorEvent.message,
        errorEvent.filename,
        errorEvent.lineno,
        errorEvent.colno,
        errorEvent.error,
      );
    if (result === true) {
      event.preventDefault();
    }
  } else {
    result = listener && listener.apply(this, arguments);
    if (
      // https://github.com/angular/angular/issues/47579
      // https://www.w3.org/TR/2011/WD-html5-20110525/history.html#beforeunloadevent
      // This is the only specific case we should check for. The spec defines that the
      // `returnValue` attribute represents the message to show the user. When the event
      // is created, this attribute must be set to the empty string.
      event.type === 'beforeunload' &&
      // To prevent any breaking changes resulting from this change, given that
      // it was already causing a significant number of failures in G3, we have hidden
      // that behavior behind a global configuration flag. Consumers can enable this
      // flag explicitly if they want the `beforeunload` event to be handled as defined
      // in the specification.
      _global[enableBeforeunloadSymbol] &&
      // The IDL event definition is `attribute DOMString returnValue`, so we check whether
      // `typeof result` is a string.
      typeof result === 'string'
    ) {
      (event as BeforeUnloadEvent).returnValue = result;
    } else if (result != undefined && !result) {
      event.preventDefault();
    }
  }

  return result;