css的弹出层

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>CSS Popup Example</title>
    <style>
        .popup {
            display: none;
            position: fixed;
            top: 50%;
            left: 50%;
            transform: translate(-50%, -50%);
            background: white;
            padding: 20px;
            box-shadow: 0 0 10px rgba(0, 0, 0, 0.3);
            z-index: 1000;
        }
        .overlay {
            display: none;
            position: fixed;
            top: 0;
            left: 0;
            width: 100%;
            height: 100%;
            background: rgba(0, 0, 0, 0.5);
            z-index: 999;
        }
        .overlay.active {
            display: block;
        }
        .popup.active {
            display: block;
        }
    </style>
</head>
<body>
    <button onclick="showPopup()">Show Popup</button>
    <div class="overlay" id="overlay"></div>
    <div class="popup" id="popup">
        <p>This is a popup!</p>
        <button onclick="hidePopup()">Close</button>
    </div>

    <script>
        function showPopup() {
            document.getElementById('popup').classList.add('active');
            document.getElementById('overlay').classList.add('active');
        }

        function hidePopup() {
            document.getElementById('popup').classList.remove('active');
            document.getElementById('overlay').classList.remove('active');
        }
    </script>
</body>
</html>

function showPopup() {
    document.getElementById('popup').classList.add('active');
    document.getElementById('overlay').classList.add('active');
}

.popup {
    position: fixed;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
}