HTML 패널

<h2>회원가입 폼</h2>

<form id="signupForm">
    <div>
        <label>아이디:</label>
        <input type="text" id="username" required>
        <span id="usernameError" class="error"></span>
    </div>
    
    <div>
        <label>비밀번호:</label>
        <input type="password" id="password" required>
        <span id="passwordError" class="error"></span>
    </div>
    
    <div>
        <label>비밀번호 확인:</label>
        <input type="password" id="passwordConfirm" required>
        <span id="confirmError" class="error"></span>
    </div>
    
    <div>
        <label>이메일:</label>
        <input type="email" id="email" required>
        <span id="emailError" class="error"></span>
    </div>
    
    <button type="submit">가입하기</button>
</form>

<div id="result"></div>

JavaScript 패널

document.getElementById('signupForm').addEventListener('submit', function(e) {
    e.preventDefault(); // 폼 제출 방지
    
    // 에러 메시지 초기화
    document.querySelectorAll('.error').forEach(e => e.textContent = '');
    
    let isValid = true;
    
    // 아이디 검증 (4자 이상)
    let username = document.getElementById('username').value;
    if (username.length < 4) {
        document.getElementById('usernameError').textContent = '아이디는 4자 이상이어야 합니다';
        isValid = false;
    }
    
    // 비밀번호 검증 (8자 이상)
    let password = document.getElementById('password').value;
    if (password.length < 8) {
        document.getElementById('passwordError').textContent = '비밀번호는 8자 이상이어야 합니다';
        isValid = false;
    }
    
    // 비밀번호 확인
    let passwordConfirm = document.getElementById('passwordConfirm').value;
    if (password !== passwordConfirm) {
        document.getElementById('confirmError').textContent = '비밀번호가 일치하지 않습니다';
        isValid = false;
    }
    
    // 이메일 검증
    let email = document.getElementById('email').value;
    if (!email.includes('@')) {
        document.getElementById('emailError').textContent = '올바른 이메일 형식이 아닙니다';
        isValid = false;
    }
    
    // 모든 검증 통과
    if (isValid) {
        document.getElementById('result').textContent = '✅ 회원가입 성공!';
        document.getElementById('result').style.color = 'green';
    }
});

CSS 패널

body {
    font-family: Arial, sans-serif;
    max-width: 400px;
    margin: 50px auto;
    padding: 20px;
}

form div {
    margin-bottom: 15px;
}

label {
    display: inline-block;
    width: 120px;
    font-weight: bold;
}

input {
    padding: 8px;
    width: 200px;
    border: 1px solid #ddd;
}

input:focus {
    border-color: #3498db;
    outline: none;
}

.error {
    display: block;
    color: red;
    font-size: 12px;
    margin-left: 120px;
    margin-top: 5px;
}

button {
    margin-left: 120px;
    padding: 10px 30px;
    background-color: #2ecc71;
    color: white;
    border: none;
    cursor: pointer;
    font-size: 16px;
}

button:hover {
    background-color: #27ae60;
}

#result {
    margin-top: 20px;
    font-size: 18px;
    font-weight: bold;
    text-align: center;
}