Google analytics script for tracking page scroll

ga: page scroll

// Google Analystics Script: Track page scroll
// All you need is to add where _gaq defined:
// https://github.com/h5bp/html5-boilerplate/wiki/ga-augments

$(function(){
  var isDuplicateScrollEvent,
    scrollTimeStart = new Date,
    $window = $(window),
    $document = $(document),
    scrollPercent;
  $window.scroll(function(){
    scrollPercent = Math.round(100*($window.height() + $window.scrollTop())/$document.height());
      if (scrollPercent > 90 && !isDuplicateScrollEvent) { //page scrolled to 90%
        isDuplicateScrollEvent = 1;
        _gaq.push(['_trackEvent', 'scrool', 
          'Window: ' + $window.height() + 'px; Document: ' + $document.height() + 'px; Time: ' + Math.round((new Date - scrollTimeStart )/1000,1) + 's',
          undefined, undefined, true
        ]);
      }
    }); 
});