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/* If is visible in viewport */
$.fn.isInViewport = function() {
  var element = this;
  var elementHeight = element.outerHeight();
  var scrollTop = $(window).scrollTop();
  var viewportHeight = $( window ).height();
  var elementOffset = element.offset();
  var inViewportHeight = elementHeight + viewportHeight;
  if ((scrollTop + viewportHeight) >  elementOffset.top && scrollTop < (elementOffset.top + elementHeight) ) {
    return (((scrollTop + viewportHeight - elementOffset.top) / inViewportHeight) * 100).toFixed(3);
  } else {
    return false;
  }
};