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workspace_javascript

performance

6.html

6.html 17.75 KB

<!DOCTYPE html>
<html lang="zh-CN">
<head>
 <meta charset="UTF-8">
 <meta name="viewport" content="width=device-width, initial-scale=1.0">
 <title>代码优化 - 虚拟滚动</title>
 <style>
 * {
 margin: 0;
 padding: 0;
 box-sizing: border-box;
 }
 body {
 font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
 background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
 min-height: 100vh;
 padding: 20px;
 }
 .container {
 max-width: 1200px;
 margin: 0 auto;
 background: white;
 border-radius: 15px;
 padding: 30px;
 box-shadow: 0 20px 60px rgba(0,0,0,0.3);
 }
 h1 {
 text-align: center;
 color: #333;
 margin-bottom: 10px;
 }
 .subtitle {
 text-align: center;
 color: #666;
 margin-bottom: 30px;
 }
 .demo-section {
 display: grid;
 grid-template-columns: 1fr 1fr;
 gap: 30px;
 margin-bottom: 30px;
 }
 .demo-box {
 border: 2px solid #e0e0e0;
 border-radius: 10px;
 padding: 20px;
 background: #f9f9f9;
 }
 .demo-box h3 {
 color: #667eea;
 margin-bottom: 15px;
 display: flex;
 align-items: center;
 gap: 10px;
 }
 .demo-box.bad {
 border-color: #ff6b6b;
 }
 .demo-box.good {
 border-color: #51cf66;
 }
 .demo-box.bad h3::before {
 content: '❌';
 }
 .demo-box.good h3::before {
 content: '✅';
 }
 .list-container {
 height: 400px;
 overflow-y: auto;
 border: 1px solid #ddd;
 border-radius: 8px;
 background: white;
 position: relative;
 }
 .list-item {
 padding: 15px;
 border-bottom: 1px solid #eee;
 display: flex;
 align-items: center;
 gap: 15px;
 transition: background 0.2s;
 }
 .list-item:hover {
 background: #f5f5f5;
 }
 .list-item .avatar {
 width: 40px;
 height: 40px;
 border-radius: 50%;
 background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
 display: flex;
 align-items: center;
 justify-content: center;
 color: white;
 font-weight: bold;
 flex-shrink: 0;
 }
 .list-item .content {
 flex: 1;
 }
 .list-item .name {
 font-weight: 600;
 color: #333;
 margin-bottom: 5px;
 }
 .list-item .email {
 color: #666;
 font-size: 14px;
 }
 .list-item .status {
 padding: 4px 12px;
 border-radius: 12px;
 font-size: 12px;
 font-weight: 500;
 }
 .list-item .status.online {
 background: #d4edda;
 color: #155724;
 }
 .list-item .status.offline {
 background: #f8d7da;
 color: #721c24;
 }
 .virtual-content {
 position: absolute;
 top: 0;
 left: 0;
 right: 0;
 }
 .controls {
 display: flex;
 gap: 10px;
 flex-wrap: wrap;
 margin-top: 15px;
 }
 button {
 padding: 10px 20px;
 border: none;
 border-radius: 5px;
 cursor: pointer;
 font-size: 14px;
 transition: all 0.3s;
 }
 .btn-primary {
 background: #667eea;
 color: white;
 }
 .btn-primary:hover {
 background: #5a6fd6;
 transform: translateY(-2px);
 }
 .btn-danger {
 background: #ff6b6b;
 color: white;
 }
 .btn-danger:hover {
 background: #fa5252;
 }
 .btn-success {
 background: #51cf66;
 color: white;
 }
 .btn-success:hover {
 background: #40c057;
 }
 .stats {
 display: grid;
 grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
 gap: 15px;
 margin-top: 20px;
 }
 .stat-card {
 background: white;
 padding: 15px;
 border-radius: 8px;
 box-shadow: 0 2px 8px rgba(0,0,0,0.1);
 text-align: center;
 }
 .stat-card h4 {
 color: #666;
 font-size: 14px;
 margin-bottom: 10px;
 }
 .stat-value {
 font-size: 24px;
 font-weight: bold;
 color: #667eea;
 }
 .stat-value.high {
 color: #ff6b6b;
 }
 .stat-value.low {
 color: #51cf66;
 }
 .code-section {
 background: #f8f9fa;
 border-radius: 10px;
 padding: 20px;
 margin-top: 30px;
 }
 .code-section h3 {
 color: #333;
 margin-bottom: 15px;
 }
 pre {
 background: #2d2d2d;
 color: #f8f8f2;
 padding: 15px;
 border-radius: 8px;
 overflow-x: auto;
 font-size: 13px;
 line-height: 1.5;
 }
 .tips {
 background: #e7f3ff;
 border-left: 4px solid #667eea;
 padding: 15px;
 margin-top: 20px;
 border-radius: 0 8px 8px 0;
 }
 .tips h4 {
 color: #667eea;
 margin-bottom: 10px;
 }
 .tips ul {
 margin-left: 20px;
 color: #555;
 }
 .tips li {
 margin: 5px 0;
 }
 .performance-info {
 background: #fff3cd;
 border-left: 4px solid #ffc107;
 padding: 15px;
 margin-top: 15px;
 border-radius: 0 8px 8px 0;
 }
 .performance-info h4 {
 color: #856404;
 margin-bottom: 10px;
 }
 .performance-info p {
 color: #856404;
 font-size: 14px;
 line-height: 1.6;
 }
 </style>
</head>
<body>
 <div class="container">
 <h1>代码优化 - 虚拟滚动</h1>
 <p class="subtitle">虚拟滚动只渲染可视区域内的元素,大幅提升长列表性能</p>

<div class="demo-section">
 <div class="demo-box bad">
 <h3>普通滚动(全部渲染)</h3>
 <div id="normalContainer" class="list-container"></div>
 <div class="performance-info">
 <h4>⚠️ 性能问题</h4>
 <p>渲染10000个DOM节点,导致页面卡顿、内存占用高</p>
 </div>
 <div class="controls">
 <button class="btn-danger" onclick="loadNormalList()">加载10000条数据</button>
 <button class="btn-primary" onclick="clearNormal()">清空</button>
 </div>
 </div>

<div class="demo-box good">
 <h3>虚拟滚动(按需渲染)</h3>
 <div id="virtualContainer" class="list-container"></div>
 <div class="performance-info" style="background: #d4edda; border-color: #28a745;">
 <h4 style="color: #155724;">✅ 性能优化</h4>
 <p>只渲染可视区域的元素,性能提升显著</p>
 </div>
 <div class="controls">
 <button class="btn-success" onclick="loadVirtualList()">加载10000条数据</button>
 <button class="btn-primary" onclick="clearVirtual()">清空</button>
 </div>
 </div>
 </div>

<div class="stats">
 <div class="stat-card">
 <h4>普通渲染DOM数量</h4>
 <div id="normalDomCount" class="stat-value high">0</div>
 </div>
 <div class="stat-card">
 <h4>虚拟渲染DOM数量</h4>
 <div id="virtualDomCount" class="stat-value low">0</div>
 </div>
 <div class="stat-card">
 <h4>DOM减少比例</h4>
 <div id="domReduction" class="stat-value">0%</div>
 </div>
 <div class="stat-card">
 <h4>数据总量</h4>
 <div id="totalData" class="stat-value">0</div>
 </div>
 </div>

<div class="code-section">
 <h3>代码实现</h3>
 <pre><code>// 虚拟滚动实现
class VirtualScroll {
 constructor(container, options = {}) {
 this.container = container;
 this.itemHeight = options.itemHeight || 70;
 this.totalItems = options.totalItems || 0;
 this.visibleCount = Math.ceil(container.offsetHeight / this.itemHeight) + 2;
 
 this.init();
 }
 
 init() {
 // 创建虚拟内容容器
 this.content = document.createElement('div');
 this.content.className = 'virtual-content';
 this.content.style.height = (this.totalItems * this.itemHeight) + 'px';
 this.container.appendChild(this.content);
 
 // 监听滚动事件
 this.container.addEventListener('scroll', () => {
 this.render();
 }, { passive: true });
 
 // 初始渲染
 this.render();
 }
 
 render() {
 const scrollTop = this.container.scrollTop;
 const startIndex = Math.floor(scrollTop / this.itemHeight);
 const endIndex = Math.min(startIndex + this.visibleCount, this.totalItems - 1);
 
 // 清空当前内容
 this.content.innerHTML = '';
 
 // 渲染可见区域的元素
 for (let i = startIndex; i <= endIndex; i++) {
 const item = this.createItem(i);
 item.style.position = 'absolute';
 item.style.top = (i * this.itemHeight) + 'px';
 item.style.left = '0';
 item.style.right = '0';
 this.content.appendChild(item);
 }
 }
 
 createItem(index) {
 const item = document.createElement('div');
 item.className = 'list-item';
 item.innerHTML = `
 <div class="avatar">${index + 1}</div>
 <div class="content">
 <div class="name">用户 ${index + 1}</div>
 <div class="email">user${index + 1}@example.com</div>
 </div>
 <div class="status ${index % 2 === 0 ? 'online' : 'offline'}">
 ${index % 2 === 0 ? '在线' : '离线'}
 </div>
 `;
 return item;
 }
 
 setData(totalItems) {
 this.totalItems = totalItems;
 this.content.style.height = (this.totalItems * this.itemHeight) + 'px';
 this.render();
 }
 
 destroy() {
 this.container.removeEventListener('scroll', this.render);
 this.content.remove();
 }
}

// 使用示例
const virtualScroll = new VirtualScroll(document.getElementById('container'), {
 itemHeight: 70,
 totalItems: 10000
});</code></pre>
 </div>

<div class="tips">
 <h4>虚拟滚动的优势</h4>
 <ul>
 <li><strong>大幅减少DOM节点</strong>:只渲染可视区域的元素,DOM节点数量大幅减少</li>
 <li><strong>提升渲染性能</strong>:减少重排重绘,提升页面流畅度</li>
 <li><strong>降低内存占用</strong>:DOM节点减少,内存占用显著降低</li>
 <li><strong>支持海量数据</strong>:可以轻松处理数万甚至数十万条数据</li>
 <li><strong>滚动流畅</strong>:滚动性能不受数据量影响</li>
 </ul>
 <h4>适用场景</h4>
 <ul>
 <li>长列表展示(用户列表、订单列表等)</li>
 <li>数据表格(大量行数据)</li>
 <li>聊天记录(历史消息)</li>
 <li>时间轴(大量时间节点)</li>
 <li>任何需要展示大量数据的场景</li>
 </ul>
 <h4>实现要点</h4>
 <ul>
 <li><strong>计算可视区域</strong>:根据容器高度和项目高度计算可见数量</li>
 <li><strong>设置总高度</strong>:使用占位元素设置正确的滚动高度</li>
 <li><strong>动态渲染</strong>:根据滚动位置动态渲染可见元素</li>
 <li><strong>性能优化</strong>:使用passive事件监听器,避免阻塞滚动</li>
 <li><strong>预加载</strong>:多渲染几个元素,避免滚动时出现空白</li>
 </ul>
 </div>
 </div>

// 普通滚动 - 渲染所有元素
 function loadNormalList() {
 const container = document.getElementById('normalContainer');
 clearNormal();
 
 const startTime = performance.now();
 const fragment = document.createDocumentFragment();
 
 for (let i = 0; i < 10000; i++) {
 const item = document.createElement('div');
 item.className = 'list-item';
 item.innerHTML = `
 <div class="avatar">${i + 1}</div>
 <div class="content">
 <div class="name">用户 ${i + 1}</div>
 <div class="email">user${i + 1}@example.com</div>
 </div>
 <div class="status ${i % 2 === 0 ? 'online' : 'offline'}">
 ${i % 2 === 0 ? '在线' : '离线'}
 </div>
 `;
 fragment.appendChild(item);
 }
 
 container.appendChild(fragment);
 
 const endTime = performance.now();
 normalDomCount = 10000;
 totalDataCount = 10000;
 
 document.getElementById('normalDomCount').textContent = normalDomCount;
 document.getElementById('totalData').textContent = totalDataCount;
 updateStats();
 }

// 虚拟滚动 - 只渲染可见元素
 function loadVirtualList() {
 const container = document.getElementById('virtualContainer');
 clearVirtual();
 
 const itemHeight = 70;
 const totalItems = 10000;
 const containerHeight = container.offsetHeight;
 const visibleCount = Math.ceil(containerHeight / itemHeight) + 2;
 
 // 创建虚拟内容容器
 const content = document.createElement('div');
 content.className = 'virtual-content';
 content.style.height = (totalItems * itemHeight) + 'px';
 container.appendChild(content);
 
 // 渲染函数
 function render() {
 const scrollTop = container.scrollTop;
 const startIndex = Math.floor(scrollTop / itemHeight);
 const endIndex = Math.min(startIndex + visibleCount, totalItems - 1);
 
 content.innerHTML = '';
 
 for (let i = startIndex; i <= endIndex; i++) {
 const item = document.createElement('div');
 item.className = 'list-item';
 item.style.position = 'absolute';
 item.style.top = (i * itemHeight) + 'px';
 item.style.left = '0';
 item.style.right = '0';
 item.innerHTML = `
 <div class="avatar">${i + 1}</div>
 <div class="content">
 <div class="name">用户 ${i + 1}</div>
 <div class="email">user${i + 1}@example.com</div>
 </div>
 <div class="status ${i % 2 === 0 ? 'online' : 'offline'}">
 ${i % 2 === 0 ? '在线' : '离线'}
 </div>
 `;
 content.appendChild(item);
 }
 
 virtualDomCount = endIndex - startIndex + 1;
 document.getElementById('virtualDomCount').textContent = virtualDomCount;
 updateStats();
 }
 
 // 监听滚动事件
 container.addEventListener('scroll', render, { passive: true });
 
 // 初始渲染
 render();
 
 totalDataCount = 10000;
 document.getElementById('totalData').textContent = totalDataCount;
 }

function clearNormal() {
 document.getElementById('normalContainer').innerHTML = '';
 normalDomCount = 0;
 document.getElementById('normalDomCount').textContent = 0;
 updateStats();
 }

function clearVirtual() {
 const container = document.getElementById('virtualContainer');
 container.innerHTML = '';
 container.removeEventListener('scroll', () => {});
 virtualDomCount = 0;
 document.getElementById('virtualDomCount').textContent = 0;
 updateStats();
 }

function updateStats() {
 if (normalDomCount > 0 && virtualDomCount > 0) {
 const reduction = ((normalDomCount - virtualDomCount) / normalDomCount * 100).toFixed(1);
 document.getElementById('domReduction').textContent = reduction + '%';
 }
 }
 </script>
</body>
</html>

Copy Edit Raw Blame History

弦中落宫商 authored 2023年07月20日 12:30 +08:00 . 性能优化 - 代码优化 - 虚拟滚动

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<!DOCTYPE html>
<html lang="zh-CN">
<head>
 <meta charset="UTF-8">
 <meta name="viewport" content="width=device-width, initial-scale=1.0">
 <title>代码优化 - 虚拟滚动</title>
 <style>
 * {
 margin: 0;
 padding: 0;
 box-sizing: border-box;
 }
 body {
 font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
 background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
 min-height: 100vh;
 padding: 20px;
 }
 .container {
 max-width: 1200px;
 margin: 0 auto;
 background: white;
 border-radius: 15px;
 padding: 30px;
 box-shadow: 0 20px 60px rgba(0,0,0,0.3);
 }
 h1 {
 text-align: center;
 color: #333;
 margin-bottom: 10px;
 }
 .subtitle {
 text-align: center;
 color: #666;
 margin-bottom: 30px;
 }
 .demo-section {
 display: grid;
 grid-template-columns: 1fr 1fr;
 gap: 30px;
 margin-bottom: 30px;
 }
 .demo-box {
 border: 2px solid #e0e0e0;
 border-radius: 10px;
 padding: 20px;
 background: #f9f9f9;
 }
 .demo-box h3 {
 color: #667eea;
 margin-bottom: 15px;
 display: flex;
 align-items: center;
 gap: 10px;
 }
 .demo-box.bad {
 border-color: #ff6b6b;
 }
 .demo-box.good {
 border-color: #51cf66;
 }
 .demo-box.bad h3::before {
 content: '❌';
 }
 .demo-box.good h3::before {
 content: '✅';
 }
 .list-container {
 height: 400px;
 overflow-y: auto;
 border: 1px solid #ddd;
 border-radius: 8px;
 background: white;
 position: relative;
 }
 .list-item {
 padding: 15px;
 border-bottom: 1px solid #eee;
 display: flex;
 align-items: center;
 gap: 15px;
 transition: background 0.2s;
 }
 .list-item:hover {
 background: #f5f5f5;
 }
 .list-item .avatar {
 width: 40px;
 height: 40px;
 border-radius: 50%;
 background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
 display: flex;
 align-items: center;
 justify-content: center;
 color: white;
 font-weight: bold;
 flex-shrink: 0;
 }
 .list-item .content {
 flex: 1;
 }
 .list-item .name {
 font-weight: 600;
 color: #333;
 margin-bottom: 5px;
 }
 .list-item .email {
 color: #666;
 font-size: 14px;
 }
 .list-item .status {
 padding: 4px 12px;
 border-radius: 12px;
 font-size: 12px;
 font-weight: 500;
 }
 .list-item .status.online {
 background: #d4edda;
 color: #155724;
 }
 .list-item .status.offline {
 background: #f8d7da;
 color: #721c24;
 }
 .virtual-content {
 position: absolute;
 top: 0;
 left: 0;
 right: 0;
 }
 .controls {
 display: flex;
 gap: 10px;
 flex-wrap: wrap;
 margin-top: 15px;
 }
 button {
 padding: 10px 20px;
 border: none;
 border-radius: 5px;
 cursor: pointer;
 font-size: 14px;
 transition: all 0.3s;
 }
 .btn-primary {
 background: #667eea;
 color: white;
 }
 .btn-primary:hover {
 background: #5a6fd6;
 transform: translateY(-2px);
 }
 .btn-danger {
 background: #ff6b6b;
 color: white;
 }
 .btn-danger:hover {
 background: #fa5252;
 }
 .btn-success {
 background: #51cf66;
 color: white;
 }
 .btn-success:hover {
 background: #40c057;
 }
 .stats {
 display: grid;
 grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
 gap: 15px;
 margin-top: 20px;
 }
 .stat-card {
 background: white;
 padding: 15px;
 border-radius: 8px;
 box-shadow: 0 2px 8px rgba(0,0,0,0.1);
 text-align: center;
 }
 .stat-card h4 {
 color: #666;
 font-size: 14px;
 margin-bottom: 10px;
 }
 .stat-value {
 font-size: 24px;
 font-weight: bold;
 color: #667eea;
 }
 .stat-value.high {
 color: #ff6b6b;
 }
 .stat-value.low {
 color: #51cf66;
 }
 .code-section {
 background: #f8f9fa;
 border-radius: 10px;
 padding: 20px;
 margin-top: 30px;
 }
 .code-section h3 {
 color: #333;
 margin-bottom: 15px;
 }
 pre {
 background: #2d2d2d;
 color: #f8f8f2;
 padding: 15px;
 border-radius: 8px;
 overflow-x: auto;
 font-size: 13px;
 line-height: 1.5;
 }
 .tips {
 background: #e7f3ff;
 border-left: 4px solid #667eea;
 padding: 15px;
 margin-top: 20px;
 border-radius: 0 8px 8px 0;
 }
 .tips h4 {
 color: #667eea;
 margin-bottom: 10px;
 }
 .tips ul {
 margin-left: 20px;
 color: #555;
 }
 .tips li {
 margin: 5px 0;
 }
 .performance-info {
 background: #fff3cd;
 border-left: 4px solid #ffc107;
 padding: 15px;
 margin-top: 15px;
 border-radius: 0 8px 8px 0;
 }
 .performance-info h4 {
 color: #856404;
 margin-bottom: 10px;
 }
 .performance-info p {
 color: #856404;
 font-size: 14px;
 line-height: 1.6;
 }
 </style>
</head>
<body>
 <div class="container">
 <h1>代码优化 - 虚拟滚动</h1>
 <p class="subtitle">虚拟滚动只渲染可视区域内的元素,大幅提升长列表性能</p>

 <div class="demo-section">
 <div class="demo-box bad">
 <h3>普通滚动(全部渲染)</h3>
 <div id="normalContainer" class="list-container"></div>
 <div class="performance-info">
 <h4>⚠️ 性能问题</h4>
 <p>渲染10000个DOM节点,导致页面卡顿、内存占用高</p>
 </div>
 <div class="controls">
 <button class="btn-danger" onclick="loadNormalList()">加载10000条数据</button>
 <button class="btn-primary" onclick="clearNormal()">清空</button>
 </div>
 </div>

 <div class="demo-box good">
 <h3>虚拟滚动(按需渲染)</h3>
 <div id="virtualContainer" class="list-container"></div>
 <div class="performance-info" style="background: #d4edda; border-color: #28a745;">
 <h4 style="color: #155724;">✅ 性能优化</h4>
 <p>只渲染可视区域的元素,性能提升显著</p>
 </div>
 <div class="controls">
 <button class="btn-success" onclick="loadVirtualList()">加载10000条数据</button>
 <button class="btn-primary" onclick="clearVirtual()">清空</button>
 </div>
 </div>
 </div>

 <div class="stats">
 <div class="stat-card">
 <h4>普通渲染DOM数量</h4>
 <div id="normalDomCount" class="stat-value high">0</div>
 </div>
 <div class="stat-card">
 <h4>虚拟渲染DOM数量</h4>
 <div id="virtualDomCount" class="stat-value low">0</div>
 </div>
 <div class="stat-card">
 <h4>DOM减少比例</h4>
 <div id="domReduction" class="stat-value">0%</div>
 </div>
 <div class="stat-card">
 <h4>数据总量</h4>
 <div id="totalData" class="stat-value">0</div>
 </div>
 </div>

 <div class="code-section">
 <h3>代码实现</h3>
 <pre><code>// 虚拟滚动实现
class VirtualScroll {
 constructor(container, options = {}) {
 this.container = container;
 this.itemHeight = options.itemHeight || 70;
 this.totalItems = options.totalItems || 0;
 this.visibleCount = Math.ceil(container.offsetHeight / this.itemHeight) + 2;
 
 this.init();
 }
 
 init() {
 // 创建虚拟内容容器
 this.content = document.createElement('div');
 this.content.className = 'virtual-content';
 this.content.style.height = (this.totalItems * this.itemHeight) + 'px';
 this.container.appendChild(this.content);
 
 // 监听滚动事件
 this.container.addEventListener('scroll', () => {
 this.render();
 }, { passive: true });
 
 // 初始渲染
 this.render();
 }
 
 render() {
 const scrollTop = this.container.scrollTop;
 const startIndex = Math.floor(scrollTop / this.itemHeight);
 const endIndex = Math.min(startIndex + this.visibleCount, this.totalItems - 1);
 
 // 清空当前内容
 this.content.innerHTML = '';
 
 // 渲染可见区域的元素
 for (let i = startIndex; i <= endIndex; i++) {
 const item = this.createItem(i);
 item.style.position = 'absolute';
 item.style.top = (i * this.itemHeight) + 'px';
 item.style.left = '0';
 item.style.right = '0';
 this.content.appendChild(item);
 }
 }
 
 createItem(index) {
 const item = document.createElement('div');
 item.className = 'list-item';
 item.innerHTML = `
 <div class="avatar">${index + 1}</div>
 <div class="content">
 <div class="name">用户 ${index + 1}</div>
 <div class="email">user${index + 1}@example.com</div>
 </div>
 <div class="status ${index % 2 === 0 ? 'online' : 'offline'}">
 ${index % 2 === 0 ? '在线' : '离线'}
 </div>
 `;
 return item;
 }
 
 setData(totalItems) {
 this.totalItems = totalItems;
 this.content.style.height = (this.totalItems * this.itemHeight) + 'px';
 this.render();
 }
 
 destroy() {
 this.container.removeEventListener('scroll', this.render);
 this.content.remove();
 }
}

// 使用示例
const virtualScroll = new VirtualScroll(document.getElementById('container'), {
 itemHeight: 70,
 totalItems: 10000
});</code></pre>
 </div>

 <div class="tips">
 <h4>虚拟滚动的优势</h4>
 <ul>
 <li><strong>大幅减少DOM节点</strong>:只渲染可视区域的元素,DOM节点数量大幅减少</li>
 <li><strong>提升渲染性能</strong>:减少重排重绘,提升页面流畅度</li>
 <li><strong>降低内存占用</strong>:DOM节点减少,内存占用显著降低</li>
 <li><strong>支持海量数据</strong>:可以轻松处理数万甚至数十万条数据</li>
 <li><strong>滚动流畅</strong>:滚动性能不受数据量影响</li>
 </ul>
 <h4>适用场景</h4>
 <ul>
 <li>长列表展示(用户列表、订单列表等)</li>
 <li>数据表格(大量行数据)</li>
 <li>聊天记录(历史消息)</li>
 <li>时间轴(大量时间节点)</li>
 <li>任何需要展示大量数据的场景</li>
 </ul>
 <h4>实现要点</h4>
 <ul>
 <li><strong>计算可视区域</strong>:根据容器高度和项目高度计算可见数量</li>
 <li><strong>设置总高度</strong>:使用占位元素设置正确的滚动高度</li>
 <li><strong>动态渲染</strong>:根据滚动位置动态渲染可见元素</li>
 <li><strong>性能优化</strong>:使用passive事件监听器,避免阻塞滚动</li>
 <li><strong>预加载</strong>:多渲染几个元素,避免滚动时出现空白</li>
 </ul>
 </div>
 </div>

 <script>
 let normalDomCount = 0;
 let virtualDomCount = 0;
 let totalDataCount = 0;

 // 普通滚动 - 渲染所有元素
 function loadNormalList() {
 const container = document.getElementById('normalContainer');
 clearNormal();
 
 const startTime = performance.now();
 const fragment = document.createDocumentFragment();
 
 for (let i = 0; i < 10000; i++) {
 const item = document.createElement('div');
 item.className = 'list-item';
 item.innerHTML = `
 <div class="avatar">${i + 1}</div>
 <div class="content">
 <div class="name">用户 ${i + 1}</div>
 <div class="email">user${i + 1}@example.com</div>
 </div>
 <div class="status ${i % 2 === 0 ? 'online' : 'offline'}">
${i % 2 === 0 ? '在线' : '离线'}
 </div>
 `;
 fragment.appendChild(item);
 }
 
 container.appendChild(fragment);
 
 const endTime = performance.now();
 normalDomCount = 10000;
 totalDataCount = 10000;
 
 document.getElementById('normalDomCount').textContent = normalDomCount;
 document.getElementById('totalData').textContent = totalDataCount;
 updateStats();
 }

 // 虚拟滚动 - 只渲染可见元素
 function loadVirtualList() {
 const container = document.getElementById('virtualContainer');
 clearVirtual();
 
 const itemHeight = 70;
 const totalItems = 10000;
 const containerHeight = container.offsetHeight;
 const visibleCount = Math.ceil(containerHeight / itemHeight) + 2;
 
 // 创建虚拟内容容器
 const content = document.createElement('div');
 content.className = 'virtual-content';
 content.style.height = (totalItems * itemHeight) + 'px';
 container.appendChild(content);
 
 // 渲染函数
 function render() {
 const scrollTop = container.scrollTop;
 const startIndex = Math.floor(scrollTop / itemHeight);
 const endIndex = Math.min(startIndex + visibleCount, totalItems - 1);
 
 content.innerHTML = '';
 
 for (let i = startIndex; i <= endIndex; i++) {
 const item = document.createElement('div');
 item.className = 'list-item';
 item.style.position = 'absolute';
 item.style.top = (i * itemHeight) + 'px';
 item.style.left = '0';
 item.style.right = '0';
 item.innerHTML = `
 <div class="avatar">${i + 1}</div>
 <div class="content">
 <div class="name">用户 ${i + 1}</div>
 <div class="email">user${i + 1}@example.com</div>
 </div>
 <div class="status ${i % 2 === 0 ? 'online' : 'offline'}">
${i % 2 === 0 ? '在线' : '离线'}
 </div>
 `;
 content.appendChild(item);
 }
 
 virtualDomCount = endIndex - startIndex + 1;
 document.getElementById('virtualDomCount').textContent = virtualDomCount;
 updateStats();
 }
 
 // 监听滚动事件
 container.addEventListener('scroll', render, { passive: true });
 
 // 初始渲染
 render();
 
 totalDataCount = 10000;
 document.getElementById('totalData').textContent = totalDataCount;
 }

 function clearNormal() {
 document.getElementById('normalContainer').innerHTML = '';
 normalDomCount = 0;
 document.getElementById('normalDomCount').textContent = 0;
 updateStats();
 }

 function clearVirtual() {
 const container = document.getElementById('virtualContainer');
 container.innerHTML = '';
 container.removeEventListener('scroll', () => {});
 virtualDomCount = 0;
 document.getElementById('virtualDomCount').textContent = 0;
 updateStats();
 }

 function updateStats() {
 if (normalDomCount > 0 && virtualDomCount > 0) {
 const reduction = ((normalDomCount - virtualDomCount) / normalDomCount * 100).toFixed(1);
 document.getElementById('domReduction').textContent = reduction + '%';
 }
 }
 </script>
</body>
</html>