test.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Dark/White Mode Toggle</title>
    <style>
        body {
            transition: background-color 0.3s, color 0.3s;
        }

        .dark-mode {
            background-color: #121212;
            color: #ffffff;
        }

        .light-mode {
            background-color: #ffffff;
            color: #000000;
        }

        .toggle-button {
            padding: 10px 20px;
            margin: 20px;
            border: none;
            border-radius: 5px;
            cursor: pointer;
            font-size: 16px;
        }

        .toggle-button.dark {
            background-color: #ffffff;
            color: #121212;
        }

        .toggle-button.light {
            background-color: #121212;
            color: #ffffff;
        }
    </style>
</head>
<body class="light-mode">
    <button id="toggleButton" class="toggle-button dark">Switch to Dark Mode</button>

    <script>
        const toggleButton = document.getElementById('toggleButton');
        const body = document.body;

        toggleButton.addEventListener('click', () => {
            if (body.classList.contains('light-mode')) {
                body.classList.replace('light-mode', 'dark-mode');
                toggleButton.textContent = 'Switch to Light Mode';
                toggleButton.classList.replace('dark', 'light');
            } else {
                body.classList.replace('dark-mode', 'light-mode');
                toggleButton.textContent = 'Switch to Dark Mode';
                toggleButton.classList.replace('light', 'dark');
            }
        });
    </script>
</body>
</html>