Fire Custom Optimizley Event at 25% Scroll Depth

gistfile1.js

$(document).ready(function(){
(function($){

	var timeoutID; 
	var scrolledTo25Pct = false;

	function stopCheck() { 
		timeoutID = null; 
	}

	function checkScroll() { 
		var bottom = $(window).height() + $(window).scrollTop(); 
		var height = $(document).height(); 
		var percentage = Math.round(100*bottom/height); 
		if (percentage > 25 && !scrolledTo25Pct) { 
			scrolledTo25Pct = true; 
			stopCheck(); 
			window['optimizely'] = window['optimizely'] || []; 
			window.optimizely.push(["trackEvent", "scroll_twenty_five"]); 
		} 
	}

	function startTimer() { 
		timeoutID = window.setTimeout(checkScroll, 10000); 
	}

	startTimer();

})(window.$);
});