prac.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <link href="/prac.css" rel="stylesheet">
</head>
<body>
    <nav>
        <h2>Logoo</h2>
        <ul>
            <li><a>Home</a></li>
            <li><a>About</a></li>
            <li><a>Post</a></li>
            <li><a>Logout</a></li>
        </ul>
        <button class="dropdown" onclick="myFunc()">Dropdown</button>
    </nav>
    <script>
        function myFunc()
        {
            var x=document.querySelector("ul");
            if(x.style.display==="none")
            {
                x.style.display='block';
            }
            else{
                x.style.display="none";
            }
        }
    </script>
</body>
</html>