HTML代码大全：从基础标签到现代Web组件的完整参考指南-Vc博客

摘要：
在2025年的Web开发中，HTML已经远远超越了简单的标记语言范畴。从语义化标签到Web Components，从多媒体嵌入到性能优化，现代HTML为开发者提供了强大的工具集。本文将为您呈现一份完整的HTML代码参考大全，涵盖从基础语法到高级特性的所有内容，每个示例都经过精心设计并可直接使用。

一、 HTML基础结构与元数据

1.1 标准HTML5文档结构

<!DOCTYPE html>
<html lang="zh-CN">
<head>
    <!-- 字符编码 -->
    <meta charset="UTF-8">
    
    <!-- 视口设置，响应式设计必备 -->
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    
    <!-- 页面标题 -->
    <title>我的网站 - 专业Web解决方案</title>
    
    <!-- 页面描述，SEO重要 -->
    <meta name="description" content="提供专业的Web开发和设计服务">
    
    <!-- 关键词 -->
    <meta name="keywords" content="Web开发, 前端, HTML, CSS, JavaScript">
    
    <!-- 作者信息 -->
    <meta name="author" content="你的名字">
    
    <!-- 开启主题色 -->
    <meta name="theme-color" content="#667eea">
    
    <!-- 禁止电话号自动识别（移动端） -->
    <meta name="format-detection" content="telephone=no">
    
    <!-- 禁止邮箱自动识别 -->
    <meta name="format-detection" content="email=no">
    
    <!-- 禁止地址自动识别 -->
    <meta name="format-detection" content="address=no">
    
    <!-- 优先使用最新IE版本 -->
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    
    <!-- 禁止百度转码 -->
    <meta http-equiv="Cache-Control" content="no-siteapp">
    
    <!-- 引入CSS文件 -->
    <link rel="stylesheet" href="styles.css">
    
    <!-- 网站图标 -->
    <link rel="icon" href="favicon.ico" type="image/x-icon">
    <link rel="apple-touch-icon" href="apple-touch-icon.png">
    
    <!-- 预加载关键资源 -->
    <link rel="preload" href="critical.css" as="style">
    <link rel="preload" href="hero-image.jpg" as="image">
    
    <!-- DNS预连接 -->
    <link rel="preconnect" href="https://fonts.googleapis.com">
    <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin>
    
    <!-- 引入Google字体 -->
    <link href="https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700&display=swap" rel="stylesheet">
</head>
<body>
    <!-- 页面内容从这里开始 -->
    <header>
        <nav>
            <!-- 导航内容 -->
        </nav>
    </header>
    
    <main>
        <!-- 主要内容 -->
    </main>
    
    <footer>
        <!-- 页脚内容 -->
    </footer>
    
    <!-- 引入JavaScript文件 -->
    <script src="script.js" defer></script>
</body>
</html>

1.2 语义化头部优化

<!-- 开放图谱协议（社交媒体分享） -->
<meta property="og:title" content="页面标题">
<meta property="og:description" content="页面描述">
<meta property="og:image" content="https://example.com/image.jpg">
<meta property="og:url" content="https://example.com">
<meta property="og:type" content="website">
<meta property="og:site_name" content="网站名称">

<!-- Twitter卡片 -->
<meta name="twitter:card" content="summary_large_image">
<meta name="twitter:title" content="页面标题">
<meta name="twitter:description" content="页面描述">
<meta name="twitter:image" content="https://example.com/image.jpg">
<meta name="twitter:site" content="@username">

<!-- 结构化数据（JSON-LD格式） -->
<script type="application/ld+json">
{
  "@context": "https://schema.org",
  "@type": "Article",
  "headline": "文章标题",
  "description": "文章描述",
  "image": "https://example.com/image.jpg",
  "author": {
    "@type": "Person",
    "name": "作者姓名"
  },
  "publisher": {
    "@type": "Organization",
    "name": "发布者名称",
    "logo": {
      "@type": "ImageObject",
      "url": "https://example.com/logo.jpg"
    }
  },
  "datePublished": "2024-01-01",
  "dateModified": "2024-01-02"
}
</script>

二、语义化布局标签

2.1 现代页面布局结构

<!DOCTYPE html>
<html lang="zh-CN">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>语义化布局示例</title>
    <style>
        * {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
        }
        
        body {
            font-family: 'Inter', sans-serif;
            line-height: 1.6;
            color: #333;
        }
        
        header, nav, main, aside, footer, section, article {
            padding: 20px;
            margin: 10px 0;
        }
        
        header { background: #2c3e50; color: white; }
        nav { background: #34495e; color: white; }
        main { background: #ecf0f1; min-height: 400px; }
        aside { background: #bdc3c7; }
        footer { background: #2c3e50; color: white; text-align: center; }
        section { background: white; margin: 20px 0; border-radius: 8px; }
        article { background: #f8f9fa; margin: 15px 0; padding: 15px; border-left: 4px solid #3498db; }
    </style>
</head>
<body>
    <!-- 页面头部 -->
    <header role="banner">
        <h1>网站标题</h1>
        <p>网站描述或标语</p>
    </header>
    
    <!-- 导航区域 -->
    <nav role="navigation" aria-label="主导航">
        <ul>
            <li><a href="#home">首页</a></li>
            <li><a href="#about">关于我们</a></li>
            <li><a href="#services">服务</a></li>
            <li><a href="#contact">联系我们</a></li>
        </ul>
    </nav>
    
    <!-- 主要内容区域 -->
    <main role="main">
        <!-- 横幅区域 -->
        <section aria-labelledby="banner-heading">
            <h2 id="banner-heading">欢迎来到我们的网站</h2>
            <p>这是一个使用语义化HTML标签构建的现代化网页布局。</p>
        </section>
        
        <!-- 特性展示 -->
        <section aria-labelledby="features-heading">
            <h2 id="features-heading">我们的特性</h2>
            
            <article>
                <h3>响应式设计</h3>
                <p>确保网站在所有设备上都能完美显示。</p>
                <time datetime="2024-01-01">发布于 2024年1月1日</time>
            </article>
            
            <article>
                <h3>高性能</h3>
                <p>优化的代码确保快速加载速度。</p>
                <time datetime="2024-01-02">发布于 2024年1月2日</time>
            </article>
            
            <article>
                <h3>无障碍访问</h3>
                <p>遵循WCAG指南，确保所有人都能访问。</p>
                <time datetime="2024-01-03">发布于 2024年1月3日</time>
            </article>
        </section>
        
        <!-- 侧边内容 -->
        <aside role="complementary" aria-labelledby="sidebar-heading">
            <h3 id="sidebar-heading">相关链接</h3>
            <nav aria-label="侧边栏导航">
                <ul>
                    <li><a href="#blog">博客</a></li>
                    <li><a href="#portfolio">作品集</a></li>
                    <li><a href="#testimonials">客户评价</a></li>
                </ul>
            </nav>
        </aside>
    </main>
    
    <!-- 页脚 -->
    <footer role="contentinfo">
        <p>&copy; 2024 我的网站. 保留所有权利.</p>
        <address>
            联系我们: <a href="mailto:info@example.com">info@example.com</a>
        </address>
    </footer>
</body>
</html>

2.2 高级布局模式

<!-- 圣杯布局 -->
<div class="holy-grail">
    <header>头部</header>
    <div class="container">
        <main>主要内容</main>
        <nav class="left-sidebar">左侧边栏</nav>
        <aside class="right-sidebar">右侧边栏</aside>
    </div>
    <footer>页脚</footer>
</div>

<style>
.holy-grail {
    display: flex;
    flex-direction: column;
    min-height: 100vh;
}

.holy-grail .container {
    display: flex;
    flex: 1;
}

.holy-grail main {
    flex: 1;
    order: 2;
}

.holy-grail .left-sidebar {
    width: 200px;
    order: 1;
}

.holy-grail .right-sidebar {
    width: 200px;
    order: 3;
}

@media (max-width: 768px) {
    .holy-grail .container {
        flex-direction: column;
    }
    
    .holy-grail .left-sidebar,
    .holy-grail .right-sidebar {
        width: 100%;
        order: 3;
    }
}
</style>

三、表单与用户输入

3.1 现代化表单设计

<!DOCTYPE html>
<html lang="zh-CN">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>现代化表单示例</title>
    <style>
        :root {
            --primary-color: #667eea;
            --error-color: #e74c3c;
            --success-color: #2ecc71;
            --border-radius: 8px;
        }
        
        .form-container {
            max-width: 600px;
            margin: 50px auto;
            padding: 30px;
            background: white;
            border-radius: 15px;
            box-shadow: 0 15px 35px rgba(0,0,0,0.1);
        }
        
        .form-group {
            margin-bottom: 25px;
            position: relative;
        }
        
        .form-label {
            display: block;
            margin-bottom: 8px;
            font-weight: 600;
            color: #2d3748;
        }
        
        .form-input {
            width: 100%;
            padding: 12px 15px;
            border: 2px solid #e2e8f0;
            border-radius: var(--border-radius);
            font-size: 16px;
            transition: all 0.3s ease;
            background: #f8f9fa;
        }
        
        .form-input:focus {
            outline: none;
            border-color: var(--primary-color);
            background: white;
            box-shadow: 0 0 0 3px rgba(102, 126, 234, 0.1);
        }
        
        .form-input:invalid {
            border-color: var(--error-color);
        }
        
        .form-input:valid {
            border-color: var(--success-color);
        }
        
        .error-message {
            color: var(--error-color);
            font-size: 14px;
            margin-top: 5px;
            display: none;
        }
        
        .form-input:invalid + .error-message {
            display: block;
        }
        
        .submit-btn {
            background: var(--primary-color);
            color: white;
            border: none;
            padding: 15px 30px;
            border-radius: var(--border-radius);
            font-size: 16px;
            cursor: pointer;
            transition: all 0.3s ease;
            width: 100%;
        }
        
        .submit-btn:hover {
            background: #5a6fd8;
            transform: translateY(-2px);
            box-shadow: 0 10px 25px rgba(102, 126, 234, 0.3);
        }
        
        .required::after {
            content: " *";
            color: var(--error-color);
        }
    </style>
</head>
<body>
    <div class="form-container">
        <h1>用户注册</h1>
        <form id="registrationForm" novalidate>
            <!-- 文本输入 -->
            <div class="form-group">
                <label for="username" class="form-label required">用户名</label>
                <input type="text" id="username" name="username" class="form-input" 
                       required minlength="3" maxlength="20"
                       pattern="[a-zA-Z0-9_]+"
                       placeholder="请输入用户名（3-20个字符）">
                <div class="error-message">用户名必须是3-20个字母、数字或下划线</div>
            </div>
            
            <!-- 邮箱输入 -->
            <div class="form-group">
                <label for="email" class="form-label required">电子邮箱</label>
                <input type="email" id="email" name="email" class="form-input"
                       required placeholder="请输入有效的电子邮箱">
                <div class="error-message">请输入有效的电子邮箱地址</div>
            </div>
            
            <!-- 密码输入 -->
            <div class="form-group">
                <label for="password" class="form-label required">密码</label>
                <input type="password" id="password" name="password" class="form-input"
                       required minlength="8"
                       pattern="^(?=.*[a-z])(?=.*[A-Z])(?=.*\d).{8,}$"
                       placeholder="至少8位，包含大小写字母和数字">
                <div class="error-message">密码必须包含大小写字母和数字，至少8位</div>
            </div>
            
            <!-- 电话号码 -->
            <div class="form-group">
                <label for="phone" class="form-label">手机号码</label>
                <input type="tel" id="phone" name="phone" class="form-input"
                       pattern="[0-9]{11}" placeholder="请输入11位手机号码">
                <div class="error-message">请输入有效的11位手机号码</div>
            </div>
            
            <!-- 日期选择 -->
            <div class="form-group">
                <label for="birthdate" class="form-label">出生日期</label>
                <input type="date" id="birthdate" name="birthdate" class="form-input"
                       min="1900-01-01" max="2024-12-31">
            </div>
            
            <!-- 范围选择 -->
            <div class="form-group">
                <label for="volume" class="form-label">音量大小</label>
                <input type="range" id="volume" name="volume" class="form-input"
                       min="0" max="100" value="50" step="10">
                <output for="volume">50</output>
            </div>
            
            <!-- 颜色选择 -->
            <div class="form-group">
                <label for="color" class="form-label">主题颜色</label>
                <input type="color" id="color" name="color" class="form-input" value="#667eea">
            </div>
            
            <!-- 文件上传 -->
            <div class="form-group">
                <label for="avatar" class="form-label">头像上传</label>
                <input type="file" id="avatar" name="avatar" class="form-input"
                       accept="image/jpeg, image/png, image/gif"
                       multiple>
            </div>
            
            <!-- 下拉选择 -->
            <div class="form-group">
                <label for="country" class="form-label">国家/地区</label>
                <select id="country" name="country" class="form-input" required>
                    <option value="">请选择国家/地区</option>
                    <option value="CN">中国</option>
                    <option value="US">美国</option>
                    <option value="JP">日本</option>
                    <option value="KR">韩国</option>
                </select>
            </div>
            
            <!-- 多选下拉 -->
            <div class="form-group">
                <label for="skills" class="form-label">技能选择</label>
                <select id="skills" name="skills" class="form-input" multiple size="4">
                    <option value="html">HTML</option>
                    <option value="css">CSS</option>
                    <option value="js">JavaScript</option>
                    <option value="react">React</option>
                    <option value="vue">Vue</option>
                    <option value="angular">Angular</option>
                </select>
            </div>
            
            <!-- 文本域 -->
            <div class="form-group">
                <label for="bio" class="form-label">个人简介</label>
                <textarea id="bio" name="bio" class="form-input" 
                         rows="4" placeholder="介绍一下你自己..."
                         maxlength="500"></textarea>
                <div class="char-count">0/500</div>
            </div>
            
            <!-- 复选框组 -->
            <fieldset class="form-group">
                <legend class="form-label">兴趣爱好</legend>
                <label>
                    <input type="checkbox" name="interests" value="reading"> 阅读
                </label>
                <label>
                    <input type="checkbox" name="interests" value="sports"> 运动
                </label>
                <label>
                    <input type="checkbox" name="interests" value="music"> 音乐
                </label>
                <label>
                    <input type="checkbox" name="interests" value="travel"> 旅行
                </label>
            </fieldset>
            
            <!-- 单选框组 -->
            <fieldset class="form-group">
                <legend class="form-label required">性别</legend>
                <label>
                    <input type="radio" name="gender" value="male" required> 男性
                </label>
                <label>
                    <input type="radio" name="gender" value="female"> 女性
                </label>
                <label>
                    <input type="radio" name="gender" value="other"> 其他
                </label>
            </fieldset>
            
            <!-- 数据列表 -->
            <div class="form-group">
                <label for="browser" class="form-label">选择浏览器</label>
                <input list="browsers" id="browser" name="browser" class="form-input"
                       placeholder="输入或选择浏览器">
                <datalist id="browsers">
                    <option value="Chrome">
                    <option value="Firefox">
                    <option value="Safari">
                    <option value="Edge">
                    <option value="Opera">
                </datalist>
            </div>
            
            <button type="submit" class="submit-btn">注册账号</button>
        </form>
    </div>

    <script>
        // 实时字符计数
        document.getElementById('bio').addEventListener('input', function(e) {
            const count = e.target.value.length;
            document.querySelector('.char-count').textContent = `${count}/500`;
        });
        
        // 范围滑块实时显示
        document.getElementById('volume').addEventListener('input', function(e) {
            e.target.nextElementSibling.textContent = e.target.value;
        });
        
        // 表单验证
        document.getElementById('registrationForm').addEventListener('submit', function(e) {
            e.preventDefault();
            if (this.checkValidity()) {
                alert('表单提交成功！');
                // 这里可以添加AJAX提交逻辑
            }
        });
    </script>
</body>
</html>

四、多媒体与图形

4.1 响应式图片与视频

<!DOCTYPE html>
<html lang="zh-CN">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>多媒体展示</title>
    <style>
        .media-container {
            max-width: 1200px;
            margin: 0 auto;
            padding: 20px;
        }
        
        .responsive-image {
            width: 100%;
            height: auto;
            border-radius: 10px;
            box-shadow: 0 10px 30px rgba(0,0,0,0.1);
        }
        
        .video-container {
            position: relative;
            width: 100%;
            padding-bottom: 56.25%; /* 16:9 宽高比 */
            margin: 20px 0;
        }
        
        .video-container video,
        .video-container iframe {
            position: absolute;
            top: 0;
            left: 0;
            width: 100%;
            height: 100%;
            border-radius: 10px;
        }
        
        .gallery {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
            gap: 15px;
            margin: 30px 0;
        }
        
        .gallery img {
            width: 100%;
            height: 200px;
            object-fit: cover;
            border-radius: 8px;
            transition: transform 0.3s ease;
            cursor: pointer;
        }
        
        .gallery img:hover {
            transform: scale(1.05);
        }
        
        figure {
            margin: 20px 0;
            text-align: center;
        }
        
        figcaption {
            margin-top: 10px;
            color: #666;
            font-style: italic;
        }
    </style>
</head>
<body>
    <div class="media-container">
        <!-- 响应式图片 -->
        <h2>响应式图片展示</h2>
        
        <!-- 使用picture元素实现艺术指导 -->
        <picture>
            <source media="(min-width: 1200px)" srcset="https://picsum.photos/1200/600">
            <source media="(min-width: 768px)" srcset="https://picsum.photos/800/400">
            <img src="https://picsum.photos/400/300" alt="描述性文字" class="responsive-image" 
                 loading="lazy" decoding="async">
        </picture>
        
        <!-- 带标题的图片 -->
        <figure>
            <img src="https://picsum.photos/800/400" alt="风景图片" class="responsive-image"
                 loading="lazy">
            <figcaption>美丽的自然风景 - 使用HTML5 figure和figcaption标签</figcaption>
        </figure>
        
        <!-- 视频播放 -->
        <h2>视频播放器</h2>
        <div class="video-container">
            <video controls poster="https://picsum.photos/800/450" preload="metadata">
                <source src="https://example.com/video.mp4" type="video/mp4">
                <source src="https://example.com/video.webm" type="video/webm">
                <track src="subtitles-zh.vtt" kind="subtitles" srclang="zh" label="中文">
                您的浏览器不支持HTML5视频播放。
            </video>
        </div>
        
        <!-- 嵌入YouTube视频 -->
        <div class="video-container">
            <iframe src="https://www.youtube.com/embed/dQw4w9WgXcQ" 
                    frameborder="0" 
                    allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" 
                    allowfullscreen
                    loading="lazy">
            </iframe>
        </div>
        
        <!-- 音频播放 -->
        <h2>音频播放器</h2>
        <audio controls style="width: 100%; margin: 20px 0;">
            <source src="audio.mp3" type="audio/mpeg">
            <source src="audio.ogg" type="audio/ogg">
            您的浏览器不支持HTML5音频播放。
        </audio>
        
        <!-- 图片画廊 -->
        <h2>图片画廊</h2>
        <div class="gallery">
            <img src="https://picsum.photos/300/200?1" alt="图片1" loading="lazy">
            <img src="https://picsum.photos/300/200?2" alt="图片2" loading="lazy">
            <img src="https://picsum.photos/300/200?3" alt="图片3" loading="lazy">
            <img src="https://picsum.photos/300/200?4" alt="图片4" loading="lazy">
            <img src="https://picsum.photos/300/200?5" alt="图片5" loading="lazy">
            <img src="https://picsum.photos/300/200?6" alt="图片6" loading="lazy">
        </div>
    </div>
</body>
</html>

4.2 SVG图形与动画

<!DOCTYPE html>
<html lang="zh-CN">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>SVG图形示例</title>
    <style>
        .svg-container {
            max-width: 800px;
            margin: 50px auto;
            padding: 20px;
            text-align: center;
        }
        
        .svg-item {
            width: 200px;
            height: 200px;
            margin: 20px;
            display: inline-block;
        }
        
        .animated-svg {
            animation: rotate 10s linear infinite;
        }
        
        @keyframes rotate {
            from { transform: rotate(0deg); }
            to { transform: rotate(360deg); }
        }
        
        .pulse {
            animation: pulse 2s ease-in-out infinite alternate;
        }
        
        @keyframes pulse {
            from { transform: scale(1); }
            to { transform: scale(1.1); }
        }
    </style>
</head>
<body>
    <div class="svg-container">
        <h1>SVG图形示例</h1>
        
        <!-- 基本形状 -->
        <div class="svg-item">
            <svg viewBox="0 0 100 100">
                <circle cx="50" cy="50" r="40" fill="#667eea" stroke="#764ba2" stroke-width="3"/>
            </svg>
            <p>圆形</p>
        </div>
        
        <div class="svg-item">
            <svg viewBox="0 0 100 100">
                <rect x="10" y="10" width="80" height="80" fill="#f093fb" rx="10"/>
            </svg>
            <p>圆角矩形</p>
        </div>
        
        <!-- 动画SVG -->
        <div class="svg-item">
            <svg viewBox="0 0 100 100" class="animated-svg">
                <polygon points="50,10 90,90 10,90" fill="#4facfe"/>
            </svg>
            <p>旋转三角形</p>
        </div>
        
        <!-- 交互式SVG -->
        <div class="svg-item">
            <svg viewBox="0 0 100 100">
                <circle cx="50" cy="50" r="40" fill="#43e97b" class="pulse"/>
                <text x="50" y="55" text-anchor="middle" fill="white" font-size="12">点击我</text>
            </svg>
            <p>脉动效果</p>
        </div>
        
        <!-- 复杂SVG图标 -->
        <div class="svg-item">
            <svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2">
                <path d="M12 2L2 7l10 5 10-5-10-5zM2 17l10 5 10-5M2 12l10 5 10-5"/>
            </svg>
            <p>图层图标</p>
        </div>
        
        <!-- SVG线条动画 -->
        <div class="svg-item">
            <svg viewBox="0 0 100 100">
                <path d="M10,50 Q50,10 90,50 T170,50" stroke="#ff6b6b" stroke-width="3" 
                      fill="none" stroke-dasharray="200" stroke-dashoffset="200">
                    <animate attributeName="stroke-dashoffset" from="200" to="0" 
                             dur="2s" fill="freeze" repeatCount="indefinite"/>
                </path>
            </svg>
            <p>线条动画</p>
        </div>
    </div>
</body>
</html>

五、高级HTML特性

5.1 Web Components

<!DOCTYPE html>
<html lang="zh-CN">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Web Components示例</title>
    <style>
        body {
            font-family: 'Inter', sans-serif;
            padding: 40px;
            background: #f5f5f5;
        }
        
        .container {
            max-width: 800px;
            margin: 0 auto;
        }
    </style>
</head>
<body>
    <div class="container">
        <h1>Web Components 示例</h1>
        
        <!-- 自定义用户卡片 -->
        <user-card 
            name="张三" 
            avatar="https://i.pravatar.cc/150?img=1"
            email="zhangsan@example.com"
            role="前端开发者">
        </user-card>
        
        <user-card 
            name="李四" 
            avatar="https://i.pravatar.cc/150?img=2"
            email="lisi@example.com"
            role="UI设计师">
        </user-card>
        
        <!-- 自定义折叠面板 -->
        <accordion-group>
            <accordion-item title="什么是Web Components?">
                Web Components是一套不同的技术，允许您创建可重用的定制元素。
            </accordion-item>
            
            <accordion-item title="Web Components的优势">
                封装性、可重用性、互操作性、标准化。
            </accordion-item>
            
            <accordion-item title="主要技术组成">
                Custom Elements、Shadow DOM、HTML Templates。
            </accordion-item>
        </accordion-group>
    </div>

    <script>
        // 用户卡片自定义元素
        class UserCard extends HTMLElement {
            constructor() {
                super();
                this.attachShadow({ mode: 'open' });
            }
            
            static get observedAttributes() {
                return ['name', 'avatar', 'email', 'role'];
            }
            
            connectedCallback() {
                this.render();
            }
            
            attributeChangedCallback() {
                this.render();
            }
            
            render() {
                const name = this.getAttribute('name') || '未知用户';
                const avatar = this.getAttribute('avatar') || 'https://i.pravatar.cc/150';
                const email = this.getAttribute('email') || '未知邮箱';
                const role = this.getAttribute('role') || '未知角色';
                
                this.shadowRoot.innerHTML = `
                    <style>
                        .user-card {
                            background: white;
                            border-radius: 15px;
                            padding: 20px;
                            margin: 15px 0;
                            box-shadow: 0 5px 15px rgba(0,0,0,0.1);
                            display: flex;
                            align-items: center;
                            transition: transform 0.3s ease;
                        }
                        
                        .user-card:hover {
                            transform: translateY(-5px);
                        }
                        
                        .avatar {
                            width: 60px;
                            height: 60px;
                            border-radius: 50%;
                            margin-right: 15px;
                            object-fit: cover;
                        }
                        
                        .info h3 {
                            margin: 0 0 5px 0;
                            color: #2d3748;
                        }
                        
                        .info p {
                            margin: 2px 0;
                            color: #718096;
                            font-size: 14px;
                        }
                    </style>
                    <div class="user-card">
                        <img src="${avatar}" alt="${name}" class="avatar">
                        <div class="info">
                            <h3>${name}</h3>
                            <p>${email}</p>
                            <p><strong>${role}</strong></p>
                        </div>
                    </div>
                `;
            }
        }
        
        customElements.define('user-card', UserCard);
        
        // 折叠面板自定义元素
        class AccordionItem extends HTMLElement {
            constructor() {
                super();
                this.attachShadow({ mode: 'open' });
            }
            
            connectedCallback() {
                this.render();
                this.addEventListener('click', this.toggle.bind(this));
            }
            
            toggle() {
                const content = this.shadowRoot.querySelector('.content');
                content.classList.toggle('active');
            }
            
            render() {
                const title = this.getAttribute('title') || '标题';
                const content = this.innerHTML;
                
                this.shadowRoot.innerHTML = `
                    <style>
                        .accordion-item {
                            border: 1px solid #e2e8f0;
                            border-radius: 8px;
                            margin: 10px 0;
                            overflow: hidden;
                        }
                        
                        .header {
                            padding: 15px 20px;
                            background: #f7fafc;
                            cursor: pointer;
                            font-weight: 600;
                            display: flex;
                            justify-content: space-between;
                            align-items: center;
                        }
                        
                        .header:hover {
                            background: #edf2f7;
                        }
                        
                        .content {
                            padding: 0 20px;
                            max-height: 0;
                            overflow: hidden;
                            transition: all 0.3s ease;
                        }
                        
                        .content.active {
                            padding: 20px;
                            max-height: 200px;
                        }
                        
                        .icon {
                            transition: transform 0.3s ease;
                        }
                        
                        .content.active + .header .icon {
                            transform: rotate(180deg);
                        }
                    </style>
                    <div class="accordion-item">
                        <div class="content">${content}</div>
                        <div class="header">
                            ${title}
                            <span class="icon">▼</span>
                        </div>
                    </div>
                `;
            }
        }
        
        customElements.define('accordion-item', AccordionItem);
        
        class AccordionGroup extends HTMLElement {
            constructor() {
                super();
            }
        }
        
        customElements.define('accordion-group', AccordionGroup);
    </script>
</body>
</html>

5.2 模板与插槽

<!DOCTYPE html>
<html lang="zh-CN">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>模板与插槽</title>
    <style>
        .card {
            border: 1px solid #ddd;
            border-radius: 8px;
            padding: 16px;
            margin: 16px;
            box-shadow: 0 2px 4px rgba(0,0,0,0.1);
        }
    </style>
</head>
<body>
    <h1>HTML模板与插槽示例</h1>
    
    <!-- 定义模板 -->
    <template id="userTemplate">
        <div class="card">
            <h2><slot name="name">默认姓名</slot></h2>
            <p><slot name="email">默认邮箱</slot></p>
            <p><slot name="bio">默认个人简介...</slot></p>
        </div>
    </template>
    
    <!-- 使用模板 -->
    <div id="userContainer"></div>
    
    <!-- 另一个模板示例 -->
    <template id="productTemplate">
        <div class="card product">
            <img slot="image" src=""  style="width: 100%; height: 200px; object-fit: cover;">
            <h3 slot="name">产品名称</h3>
            <p slot="description">产品描述</p>
            <div slot="price" class="price">¥0.00</div>
            <button slot="action">购买</button>
        </div>
    </template>
    
    <script>
        // 使用模板创建内容
        const template = document.getElementById('userTemplate');
        const container = document.getElementById('userContainer');
        
        const users = [
            { name: '张三', email: 'zhangsan@example.com', bio: '前端开发者' },
            { name: '李四', email: 'lisi@example.com', bio: 'UI设计师' },
            { name: '王五', email: 'wangwu@example.com', bio: '全栈工程师' }
        ];
        
        users.forEach(user => {
            const instance = template.content.cloneNode(true);
            
            // 填充插槽内容
            const nameSlot = instance.querySelector('slot[name="name"]');
            const emailSlot = instance.querySelector('slot[name="email"]');
            const bioSlot = instance.querySelector('slot[name="bio"]');
            
            nameSlot.textContent = user.name;
            emailSlot.textContent = user.email;
            bioSlot.textContent = user.bio;
            
            container.appendChild(instance);
        });
        
        // 动态创建模板内容
        const productTemplate = document.getElementById('productTemplate');
        const productInstance = productTemplate.content.cloneNode(true);
        
        // 设置插槽内容
        productInstance.querySelector('[slot="image"]').src = 'https://picsum.photos/300/200';
        productInstance.querySelector('[slot="name"]').textContent = '智能手机';
        productInstance.querySelector('[slot="description"]').textContent = '高性能智能手机';
        productInstance.querySelector('[slot="price"]').textContent = '¥2999.00';
        
        document.body.appendChild(productInstance);
    </script>
</body>
</html>

六、性能优化与SEO

6.1 性能优化HTML技巧

<!DOCTYPE html>
<html lang="zh-CN">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>性能优化HTML示例</title>
    
    <!-- 关键CSS内联 -->
    <style>
        /* 首屏关键CSS */
        .critical-css {
            font-family: system-ui, -apple-system, sans-serif;
            line-height: 1.6;
            color: #333;
        }
        
        .hero {
            min-height: 100vh;
            display: flex;
            align-items: center;
            justify-content: center;
            background: linear-gradient(135deg, #667eea, #764ba2);
            color: white;
        }
    </style>
    
    <!-- 预加载关键资源 -->
    <link rel="preload" href="critical.css" as="style">
    <link rel="preload" href="hero-image.webp" as="image" type="image/webp">
    <link rel="preload" href="font.woff2" as="font" type="font/woff2" crossorigin>
    
    <!-- 预连接重要域名 -->
    <link rel="preconnect" href="https://fonts.googleapis.com">
    <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin>
    
    <!-- DNS预解析 -->
    <link rel="dns-prefetch" href="https://cdn.example.com">
    
    <!-- 延迟加载非关键CSS -->
    <link rel="stylesheet" href="non-critical.css" media="print" onload="this.media='all'">
    
    <!-- 异步加载字体 -->
    <link href="https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600&display=swap" 
          rel="stylesheet" media="print" onload="this.media='all'">
</head>
<body>
    <!-- 首屏内容优先 -->
    <section class="hero">
        <h1>高性能网站</h1>
        <p>使用现代HTML技术优化性能</p>
    </section>
    
    <!-- 懒加载图片 -->
    <img src="placeholder.jpg" 
         data-src="https://picsum.photos/800/400" 
         alt="描述文字"
         loading="lazy"
         class="lazy-image">
    
    <!-- 响应式图片与WebP格式 -->
    <picture>
        <source type="image/webp" srcset="image-800.webp 800w, image-400.webp 400w">
        <source type="image/jpeg" srcset="image-800.jpg 800w, image-400.jpg 400w">
        <img src="image-400.jpg" alt="描述文字" loading="lazy">
    </picture>
    
    <!-- 延迟加载iframe -->
    <iframe src="about:blank" 
            data-src="https://www.youtube.com/embed/example" 
            loading="lazy"
            title="视频内容">
    </iframe>
    
    <!-- 结构化数据 -->
    <script type="application/ld+json">
    {
        "@context": "https://schema.org",
        "@type": "Article",
        "headline": "文章标题",
        "description": "文章描述",
        "image": "https://example.com/image.jpg",
        "author": {
            "@type": "Person",
            "name": "作者姓名"
        },
        "publisher": {
            "@type": "Organization",
            "name": "发布者",
            "logo": {
                "@type": "ImageObject",
                "url": "https://example.com/logo.jpg"
            }
        },
        "datePublished": "2024-01-01",
        "dateModified": "2024-01-02"
    }
    </script>
    
    <!-- 延迟加载脚本 -->
    <script src="non-critical.js" defer></script>
    
    <script>
        // 图片懒加载
        document.addEventListener('DOMContentLoaded', function() {
            const lazyImages = [].slice.call(document.querySelectorAll('img.lazy-image'));
            
            if ('IntersectionObserver' in window) {
                const lazyImageObserver = new IntersectionObserver(function(entries, observer) {
                    entries.forEach(function(entry) {
                        if (entry.isIntersecting) {
                            const lazyImage = entry.target;
                            lazyImage.src = lazyImage.dataset.src;
                            lazyImage.classList.remove('lazy-image');
                            lazyImageObserver.unobserve(lazyImage);
                        }
                    });
                });
                
                lazyImages.forEach(function(lazyImage) {
                    lazyImageObserver.observe(lazyImage);
                });
            }
        });
        
        // iframe懒加载
        const iframes = document.querySelectorAll('iframe[data-src]');
        iframes.forEach(iframe => {
            iframe.addEventListener('load', function() {
                iframe.src = iframe.dataset.src;
            });
        });
    </script>
</body>
</html>

七、总结：HTML最佳实践

HTML开发的核心原则：

语义化优先：使用合适的标签表达内容含义
可访问性：确保所有用户都能访问内容
性能优化：减少加载时间，提升用户体验
SEO友好：使用合适的元数据和结构化数据
响应式设计：确保在所有设备上良好显示
代码可维护：保持代码清晰、结构化

常用HTML标签速查表：

<!-- 文本标签 -->
<h1>到<h6> 标题
<p> 段落
<span> 行内容器
<strong> 重要文本
<em> 强调文本
<mark> 标记文本
<small> 小号文本
<time> 时间日期

<!-- 结构标签 -->
<header> 页头
<nav> 导航
<main> 主内容
<article> 文章
<section> 章节
<aside> 侧边栏
<footer> 页脚

<!-- 媒体标签 -->
<img> 图片
<video> 视频
<audio> 音频
<figure> 媒体组合
<figcaption> 媒体说明

<!-- 表单标签 -->
<form> 表单
<input> 输入框
<textarea> 文本域
<select> 下拉框
<button> 按钮
<label> 标签
<fieldset> 字段组
<legend> 字段组标题

<!-- 表格标签 -->
<table> 表格
<thead> 表头
<tbody> 表体
<tfoot> 表尾
<tr> 表格行
<th> 表头单元格
<td> 表格单元格

<!-- 交互标签 -->
<details> 折叠内容
<summary> 折叠标题
<dialog> 对话框
<progress> 进度条
<meter> 度量器

通过掌握这些HTML技术和最佳实践，您将能够创建出结构良好、性能优越、用户体验出色的现代网站。记住，HTML是Web开发的基石，扎实的HTML基础是成为优秀前端开发者的第一步。

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