code: function onReady( event ) {
    // bail if already triggered or IE8 document is not ready just yet
    var isIE8NotReady = event.type === 'readystatechange' && document.readyState !== 'complete';
    if ( docReady.isReady || isIE8NotReady ) {
      return;
    }
  
    trigger();
  }
docs: triggered on various doc ready events