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组件详解#12：目录导航，你的文章很长，但读者的耐心只有3秒 | Component Deep Dive #12: Table of Contents — Your Article Is Long, But Your Reader's Patience Is 3 Seconds

2026-06-24 编译员：编译员 代码产品 Web Components CSS JavaScript

本文组件来自 Web Component Dictionary v2.0 · 网页组件活字典，83组件/8分类/中英双语/实时预览/单文件无依赖。
在线体验：wdsega.github.io/web-components | 购买完整版：payhip.com/b/S9pj2 ¥9.99

3000 字的文章，读者 3 秒决定看不看

你花了 4 小时写了一篇深度技术文章。发布后，平均阅读时长 32 秒。为什么？

因为这 3000 字对读者来说是一堵墙。他不知道里面有什么，不知道值不值得花时间。目录导航（Table of Contents，TOC）就是这堵墙上的地图。

几乎所有技术文档网站都有 TOC：MDN、Vue 文档、React 文档。它不是装饰，是信息架构的一部分。

组件是什么

Web Component Dictionary v2.0 中的目录导航是一个侧边栏组件，自动提取页面标题生成目录，固定吸附在页面一侧，滚动时高亮当前阅读位置。

核心特征：

  • 自动提取 <h2> / <h3> 标题生成目录
  • 侧边栏固定（sticky），不随页面滚动消失
  • 当前阅读位置高亮（Scroll Spy）
  • 点击跳转 + 平滑滚动

代码拆解

HTML 结构

<div class="toc-container">
  <nav class="toc">
    <h3 class="toc-title">目录</h3>
    <ul class="toc-list" id="tocList">
      <!-- JS 动态生成 -->
    </ul>
  </nav>
  <main class="toc-content">
    <h2 id="intro">引言</h2>
    <h2 id="setup">环境搭建</h2>
    <h2 id="usage">使用方法</h2>
    <h2 id="advanced">高级技巧</h2>
  </main>
</div>

CSS：侧边栏吸顶

.toc-container {
  display: flex;
  gap: 40px;
  max-width: 1200px;
  margin: 0 auto;
  padding: 20px;
}

.toc {
  width: 240px;
  flex-shrink: 0;
  position: sticky;
  top: 80px;
  align-self: flex-start;
  max-height: calc(100vh - 100px);
  overflow-y: auto;
}

.toc-list a {
  display: block;
  padding: 6px 12px;
  color: #888;
  text-decoration: none;
  font-size: 14px;
  border-left: 2px solid transparent;
  transition: all 0.2s ease;
}

.toc-list a.active {
  color: #e94560;
  border-left-color: #e94560;
  background: rgba(233,69,96,0.1);
}

.toc-content {
  flex: 1;
  min-width: 0;
}

关键技巧：

  • position: sticky; top: 80px — 侧边栏吸顶，留出导航栏空间
  • align-self: flex-start — 防止 sticky 被 flex 拉伸
  • max-height: calc(100vh - 100px) — 目录太长时自己滚动
  • 活跃项用左边框高亮，视觉引导更清晰

JavaScript：动态生成 + Scroll Spy

function buildTOC() {
  const tocList = document.getElementById('tocList');
  const headings = document.querySelectorAll('.toc-content h2, .toc-content h3');
  
  headings.forEach(heading => {
    if (!heading.id) {
      heading.id = heading.textContent
        .toLowerCase().replace(/\s+/g, '-');
    }
    
    const a = document.createElement('a');
    a.href = '#' + heading.id;
    a.textContent = heading.textContent;
    a.dataset.target = heading.id;
    
    if (heading.tagName === 'H3') {
      a.style.paddingLeft = '28px';
      a.style.fontSize = '13px';
    }
    
    const li = document.createElement('li');
    li.appendChild(a);
    tocList.appendChild(li);
  });
}

// 点击平滑跳转
tocList.addEventListener('click', e => {
  if (e.target.tagName === 'A') {
    e.preventDefault();
    const target = document.getElementById(e.target.dataset.target);
    target.scrollIntoView({ behavior: 'smooth' });
  }
});

// Scroll Spy
window.addEventListener('scroll', () => {
  const headings = document.querySelectorAll('.toc-content h2, .toc-content h3');
  let current = '';
  headings.forEach(h => {
    if (window.scrollY >= h.offsetTop - 120) current = h.id;
  });
  document.querySelectorAll('.toc-list a').forEach(a => {
    a.classList.toggle('active', a.dataset.target === current);
  });
});

关键技术点深挖

sticky vs fixed

很多人用 fixed 做侧边栏。问题：fixed 脱离文档流，需要手动算 left/right，响应式布局时位置会跑偏。

sticky 的优势：保持 flex 布局中的原始位置，只”粘”在指定位置。你不需要计算 left 值——在父容器列里自然定位。响应式友好得多。

自动生成 vs 手写 HTML

自动提取的好处是零维护。但如果标题是”那些年我们追过的技术债”这种文学化风格，提取出来的目录可读性差。

推荐：自动提取 + 手动覆盖。JS 生成默认目录，支持在 HTML 里用手写的 <ul class="toc-list"> 覆盖。

移动端适配

小屏幕 240px 侧边栏太奢侈。用 @media (max-width: 768px) 把 TOC 改成顶部横排标签，或收进 <details> 折叠块：

@media (max-width: 768px) {
  .toc-container { flex-direction: column; }
  .toc { width: 100%; position: static; }
  .toc-list { display: flex; flex-wrap: wrap; gap: 8px; }
  .toc-list a { border-left: none; border-bottom: 2px solid transparent; }
  .toc-list a.active { border-bottom-color: #e94560; }
}

常见坑点

坑1：id 冲突

两个 section 都叫”使用方法” → 都生成 #使用方法 → 锚点失效。解决：检查重复后追加 -2、-3。

坑2：动态内容

SPA/MDX 页面加载时标题还不存在。buildTOC() 要放在内容加载完成的回调里。

坑3：URL hash 污染

点击 TOC 链接改变 URL。用户刷新后跳到锚点位置，但 TOC 没高亮。解决：页面加载时读取 hash，主动高亮对应目录项。

变体拓展

  1. 折叠式层级：h3 默认隐藏，点击 h2 展开
  2. 进度条版：目录项旁显示阅读进度百分比
  3. 浮窗版：移动端右下角浮窗按钮呼出目录

本文组件来自 Web Component Dictionary v2.0 — 83个开箱即用的网页组件，导航/表单/数据展示/多媒体等8大分类，中英双语，实时预览，单文件无依赖。
🔗 在线体验：wdsega.github.io/web-components
🛒 购买完整版源码（¥9.99 一次性买断）：payhip.com/b/S9pj2

Component Deep Dive #12: Table of Contents — Your Article Is Long, But Your Reader’s Patience Is 3 Seconds

3,000 Words, 3 Seconds to Decide

You spent 4 hours writing a deep technical article. Published it. Average read time: 32 seconds. Why?

Because to a reader, 3,000 words is a wall. They don’t know what’s inside. A Table of Contents is the map on that wall.

Almost every technical documentation site has a TOC: MDN, Vue docs, React docs. It’s not decoration; it’s information architecture.

What It Is

A sidebar component that auto-extracts headings, sticks to the page side, and highlights the current reading position via Scroll Spy.

Code Breakdown

HTML: A flex container with <nav class="toc"> and <main>. Headings have IDs.

CSS: position: sticky; top: 80px keeps the sidebar visible during scroll. align-self: flex-start prevents flex stretching. Active items highlight with a left border accent.

JS: buildTOC() scans <h2>/<h3> elements and builds anchor links. Click handlers use scrollIntoView({ behavior: 'smooth' }). Scroll listener updates .active class.

Key Insight: sticky > fixed

position: fixed requires manual left/right calculations that break on responsive layouts. sticky stays in its natural flex position and just sticks — no position math needed.

Auto-Generation vs Manual HTML

Auto-extraction = zero maintenance. But literary-style headings produce ugly TOC entries. Best practice: auto-generate by default, with a manual override option using pre-written <ul class="toc-list">.

Mobile Adaptation

At < 768px, restructure TOC as horizontal tag cloud or collapse into a <details> block.

Common Pitfalls

  • Duplicate IDs: Two “Usage” sections collide. Add sequential suffixes.
  • Dynamic content: In SPAs, headings may not exist at DOMContentLoaded. Call buildTOC() in content-loaded callback.
  • URL hash pollution: Handle URL hash on page load to highlight the correct TOC item.

Variants

  • Collapsible hierarchy: h3 hidden, expand on h2 click
  • Progress indicator: Reading percentage beside each item
  • Floating trigger: Corner button overlay for mobile

This component is from Web Component Dictionary v2.0 — 83 ready-to-use web components across 8 categories. Bilingual, live preview, single-file, zero dependencies.
🔗 Live demo: wdsega.github.io/web-components
🛒 Buy full source code ($9.99 one-time): payhip.com/b/S9pj2

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