Add elements

<!DOCTYPE html>  
<html>  
<head>  
    <title>JavaScript appendChild() Method</title>  
    <style>  
    </style>  
</head>   
<body>  
    <h1>CloseTag</h1>  
    <h2>JavaScript appendChild() Method</h2>  
    <ul id="languages">  
        <li>Python</li>  
        <li>Java</li>  
    <li>Data Structure</li>  
    </ul>  
    <button onclick="append()">Append</button>  
    <script>  
        function append() {  
            var node = document.createElement("LI");  
            var textnode =   
                document.createTextNode("C#");  
            node.appendChild(textnode);  
            document.getElementById("languages").appendChild(node);  
        }  
    </script>  
</body>  
</html>