jquery 弹出层居中

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>jQuery 弹出层居中示例</title>
    <style>
        #popup {
            display: none;
            position: fixed;
            top: 50%;
            left: 50%;
            transform: translate(-50%, -50%);
            width: 300px;
            height: 200px;
            background-color: white;
            border: 1px solid black;
            padding: 20px;
            box-shadow: 0 0 10px rgba(0, 0, 0, 0.5);
        }
    </style>
    <script src="https://code.jquery.com/jquery-3.6.0.min.js"></script>
</head>
<body>
    <button id="showPopup">显示弹出层</button>
    <div id="popup">
        这是一个居中的弹出层！
    </div>

    <script>
        $(document).ready(function() {
            $('#showPopup').click(function() {
                $('#popup').fadeIn();
            });
        });
    </script>
</body>
</html>