index.html

<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>test</title>
	<style>
		#div1{
			text-decoration: none;
			background-color: green;
		}
	</style>
</head>
<body>
	<button id="btn">click</button>
	<div id="div1" class="apple">
		<p id="p1">saakdjf</p>
		<p class="aa">asgeer</p>
		<h1 class="aa">q4y5</h1>
	</div>
	<ul id="ul1">
		<li class="aa">jerijqw</li>
		<li class="aa">asefew</li>
		<li class="aa">regtwe</li>
	</ul>
	<script src="myLibrary.js"></script>
	<script>
		var oBtn = document.getElementById('btn');
		var oUl = document.getElementById('ul1');
		var oDiv = document.getElementById('div1');
		var oP = document.getElementById('p1');
		
		addEvent();

		function addEvent(elem, type, handler){
			var fn = function(){
				
			}
			if(elem.addEventListener){
				return elem.addEventListener(type, fn, false);
			}
		}


	</script>
</body>
</html>