用户认证系统登录界面

下面是使用HTML和JavaScript实现的一个中文版登录界面，包含登录、注册和修改密码功能。注册成功后会显示提示信息，在登录成功后进入一个大大的欢迎页面。

1.代码展示

<!DOCTYPE html>
<html lang="zh-CN">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>用户认证系统</title>
    <style>
        body {
            font-family: Arial, sans-serif;
            display: flex;
            justify-content: center;
            align-items: center;
            height: 100vh;
            background-color: #f4f4f9;
        }
        .container {
            width: 300px;
            padding: 20px;
            background-color: white;
            box-shadow: 0 0 10px rgba(0, 0, 0, 0.1);
            border-radius: 5px;
            text-align: center;
        }
        h2 {
            margin-bottom: 20px;
        }
        form {
            display: flex;
            flex-direction: column;
        }
        input[type="text"],
        input[type="password"] {
            margin-bottom: 10px;
            padding: 10px;
            border: 1px solid #ccc;
            border-radius: 5px;
            width: 100%;
        }
        button {
            padding: 10px;
            background-color: #007bff;
            color: white;
            border: none;
            border-radius: 5px;
            cursor: pointer;
            width: 100%;
        }
        button:hover {
            background-color: #0056b3;
        }
        .message {
            margin-top: 10px;
        }
        .success {
            color: green;
        }
        .error {
            color: red;
        }
        #welcome-container {
            width: 400px;
            padding: 40px;
            background-color: #d4edda;
            box-shadow: 0 0 10px rgba(0, 0, 0, 0.1);
            border-radius: 10px;
            text-align: center;
        }
        #welcome-message {
            font-size: 24px;
            margin-bottom: 20px;
        }
    </style>
</head>
<body>
    <div class="container" id="login-container">
        <h2>登录</h2>
        <form id="login-form">
            <input type="text" id="login-username" placeholder="用户名" required>
            <input type="password" id="login-password" placeholder="密码" required>
            <button type="submit">登录</button>
        </form>
        <p class="message error" id="login-error"></p>
        <p class="message"><a href="#" onclick="showRegisterForm(); return false;">注册新账号</a></p>
    </div>

    <div class="container" id="register-container" style="display: none;">
        <h2>注册</h2>
        <form id="register-form">
            <input type="text" id="register-username" placeholder="用户名" required>
            <input type="password" id="register-password" placeholder="密码" required>
            <button type="submit">注册</button>
        </form>
        <p class="message success" id="register-success"></p>
        <p class="message error" id="register-error"></p>
        <p class="message"><a href="#" onclick="showLoginForm(); return false;">返回登录</a></p>
    </div>

    <div class="container" id="change-password-container" style="display: none;">
        <h2>修改密码</h2>
        <form id="change-password-form">
            <input type="password" id="old-password" placeholder="旧密码" required>
            <input type="password" id="new-password" placeholder="新密码" required>
            <button type="submit">修改密码</button>
        </form>
        <p class="message error" id="change-password-error"></p>
        <p class="message"><a href="#" onclick="showWelcomePage(); return false;">返回欢迎页面</a></p>
    </div>

    <div id="welcome-container" style="display: none;">
        <h2 id="welcome-message"></h2>
        <button onclick="showChangePassword()">修改密码</button>
        <button onclick="logout()">注销</button>
    </div>

    <script>
        let users = [];
        let currentUser = null;

        document.getElementById('login-form').addEventListener('submit', function(event) {
            event.preventDefault();
            const username = document.getElementById('login-username').value;
            const password = document.getElementById('login-password').value;
            const user = users.find(user => user.username === username && user.password === password);
            if (user) {
                currentUser = user;
                showWelcomePage();
            } else {
                document.getElementById('login-error').textContent = '无效的用户名或密码';
            }
        });

        document.getElementById('register-form').addEventListener('submit', function(event) {
            event.preventDefault();
            const username = document.getElementById('register-username').value;
            const password = document.getElementById('register-password').value;
            if (!users.find(user => user.username === username)) {
                users.push({ username, password });
                document.getElementById('register-success').textContent = '注册成功！';
                setTimeout(() => {
                    document.getElementById('register-success').textContent = '';
                }, 3000);
                document.getElementById('register-username').value = '';
                document.getElementById('register-password').value = '';
                showLoginForm();
            } else {
                document.getElementById('register-error').textContent = '用户名已存在';
            }
        });

        document.getElementById('change-password-form').addEventListener('submit', function(event) {
            event.preventDefault();
            const oldPassword = document.getElementById('old-password').value;
            const newPassword = document.getElementById('new-password').value;
            if (currentUser && currentUser.password === oldPassword) {
                currentUser.password = newPassword;
                users = users.map(user => 
                    user.username === currentUser.username ? { ...user, password: newPassword } : user
                );
                document.getElementById('change-password-error').textContent = '密码修改成功';
                setTimeout(() => {
                    document.getElementById('change-password-error').textContent = '';
                }, 3000);
                hideChangePassword();
            } else {
                document.getElementById('change-password-error').textContent = '旧密码不正确';
            }
        });

        function showWelcomePage() {
            document.getElementById('login-container').style.display = 'none';
            document.getElementById('register-container').style.display = 'none';
            document.getElementById('change-password-container').style.display = 'none';
            document.getElementById('welcome-container').style.display = 'block';
            document.getElementById('welcome-message').textContent = `欢迎, ${currentUser.username}`;
        }

        function logout() {
            currentUser = null;
            document.getElementById('welcome-container').style.display = 'none';
            document.getElementById('login-container').style.display = 'block';
        }

        function showRegisterForm() {
            document.getElementById('login-container').style.display = 'none';
            document.getElementById('register-container').style.display = 'block';
            document.getElementById('login-error').textContent = ''; // Clear login error message
        }

        function showLoginForm() {
            document.getElementById('register-container').style.display = 'none';
            document.getElementById('login-container').style.display = 'block';
            document.getElementById('register-success').textContent = ''; // Clear registration success message
            document.getElementById('register-error').textContent = ''; // Clear registration error message
        }

        function showChangePassword() {
            document.getElementById('welcome-container').style.display = 'none';
            document.getElementById('change-password-container').style.display = 'block';
        }

        function hideChangePassword() {
            document.getElementById('change-password-container').style.display = 'none';
            document.getElementById('welcome-container').style.display = 'block';
        }
    </script>
</body>
</html>