Unnamed

<html>
<head>
    <script>
        onload = function() {
            var el = document.getElementById('button');
            el.old_func = el.onclick;
            el.onclick = function() {  this.old_func(); alert('Cool'); }
        }
        
    </script>
</head>
<body>
    <span id="button"  value="test" onclick="alert('test')">Test</span>
</body>
</html>