Example of broken code
The javascript here fails to add an event listener to the button.
by liffiton
HTML
<html>
<head>
<script type="text/javascript">
var handleClick = function(event) {
alert("Clicked!");
};
var elem = document.querySelector("#myelement");
elem.addEventListener('click', handleClick);
</script>
</head>
<body>
<button id="myelement">
Click Me
</button>
</body>
</html>