Agora Test / ScrollTrigger_content_length

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!function(f,b,e,v,n,t,s){if(f.fbq)return;n=f.fbq=function(){n.callMethod?
n.callMethod.apply(n,arguments):n.queue.push(arguments)};if(!f._fbq)f._fbq=n;
n.push=n;n.loaded=!0;n.version='2.0';n.queue=[];t=b.createElement(e);t.async=!0;
t.src=v;s=b.getElementsByTagName(e)[0];s.parentNode.insertBefore(t,s)}(window,
document,'script','//connect.facebook.net/en_US/fbevents.js');

fbq('init', '123456');
fbq('track', 'PageView');


var executeWhenReachedPagePercentage = function(percentage, callback) {
  if (typeof percentage !== 'number') {
    console.error(
      'First parameter must be a number, got',
      typeof percentage,
      'instead',
    );
  }

  if (typeof callback !== 'function') {
    console.error(
      'Second parameter must be a function, got',
      typeof callback,
      'instead',
    );
  }

  function getDocumentLength() {
    var D = document;
    return Math.max(
        D.body.scrollHeight, D.documentElement.scrollHeight,
        D.body.offsetHeight, D.documentElement.offsetHeight,
        D.body.clientHeight, D.documentElement.clientHeight
    )
  }

  function getWindowLength() {
    return window.innerHeight ||
      (document.documentElement || document.body).clientHeight;
  }

  function getScrollableLength() {
    if (getDocumentLength() > getWindowLength()) {
      return getDocumentLength() - getWindowLength();
    } else {
      return 0;
    }
  }

  var scrollableLength = getScrollableLength();

  window.addEventListener('resize', function(){
    scrollableLength = getScrollableLength();
  }, false)

  function getCurrentScrolledLengthPosition() {
   return window.pageYOffset ||
     (document.documentElement || document.body.parentNode || document.body).scrollTop;
  }

  function getPercentageScrolled() {
    if (scrollableLength == 0) {
      return 100;
    } else {
      return getCurrentScrolledLengthPosition() / scrollableLength * 100;
    }
  }

  var executeCallback = (function() {
    var wasExecuted = false;
    return function() {
      if (!wasExecuted && getPercentageScrolled() > percentage) {
        wasExecuted = true;
        callback();
      }
    };
  })();

  if (getDocumentLength() == 0 ||
    (getWindowLength()/getDocumentLength() * 100 >= percentage)) {
    callback();
  } else {
    window.addEventListener('scroll', executeCallback, false);
  }
};executeWhenReachedPagePercentage(75, function() { fbq('trackCustom', 'content_length', {custom_param: '75%'});  });
</script>
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