jquery表单特效

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>jQuery Form Validation</title>
    <script src="https://code.jquery.com/jquery-3.6.0.min.js"></script>
    <script src="https://cdn.jsdelivr.net/npm/jquery-validation@1.19.3/dist/jquery.validate.min.js"></script>
</head>
<body>
    <form id="registrationForm">
        <label for="username">Username:</label>
        <input type="text" id="username" name="username"><br><br>
        <label for="email">Email:</label>
        <input type="email" id="email" name="email"><br><br>
        <button type="submit">Submit</button>
    </form>

    <script>
        $(document).ready(function() {
            $('#registrationForm').validate({
                rules: {
                    username: {
                        required: true,
                        minlength: 4
                    },
                    email: {
                        required: true,
                        email: true
                    }
                },
                messages: {
                    username: {
                        required: "Please enter a username",
                        minlength: "Your username must be at least 4 characters long"
                    },
                    email: "Please enter a valid email address"
                }
            });
        });
    </script>
</body>
</html>