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<title data-react-helmet="true">React Fiber 的作用和原理 | HZFE - 剑指前端 Offer</title><meta data-react-helmet="true" name="twitter:card" content="summary_large_image"><meta data-react-helmet="true" property="og:url" content="https://hzfe.github.io/awesome-interview/book2/frame-react-fiber"><meta data-react-helmet="true" name="docusaurus_locale" content="en"><meta data-react-helmet="true" name="docusaurus_version" content="current"><meta data-react-helmet="true" name="docusaurus_tag" content="docs-default-current"><meta data-react-helmet="true" property="og:title" content="React Fiber 的作用和原理 | HZFE - 剑指前端 Offer"><meta data-react-helmet="true" name="description" content="相关问题"><meta data-react-helmet="true" property="og:description" content="相关问题"><link data-react-helmet="true" rel="shortcut icon" href="/awesome-interview/img/favicon.ico"><link data-react-helmet="true" rel="canonical" href="https://hzfe.github.io/awesome-interview/book2/frame-react-fiber"><link data-react-helmet="true" rel="alternate" href="https://hzfe.github.io/awesome-interview/book2/frame-react-fiber" hreflang="en"><link data-react-helmet="true" rel="alternate" href="https://hzfe.github.io/awesome-interview/book2/frame-react-fiber" hreflang="x-default"><link rel="stylesheet" href="/awesome-interview/assets/css/styles.36d1aa8c.css">
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<div><a href="#" class="skipToContent_1oUP">Skip to main content</a></div><nav class="navbar navbar--fixed-top"><div class="navbar__inner"><div class="navbar__items"><button aria-label="Navigation bar toggle" class="navbar__toggle clean-btn" type="button" tabindex="0"><svg width="30" height="30" viewBox="0 0 30 30" aria-hidden="true"><path stroke="currentColor" stroke-linecap="round" stroke-miterlimit="10" stroke-width="2" d="M4 7h22M4 15h22M4 23h22"></path></svg></button><a class="navbar__brand" href="/awesome-interview/"><img src="/awesome-interview/img/badge.svg" alt="HZFE" class="themedImage_1VuW themedImage--light_3UqQ navbar__logo"><img src="/awesome-interview/img/badge.svg" alt="HZFE" class="themedImage_1VuW themedImage--dark_hz6m navbar__logo"><b class="navbar__title">剑指前端 Offer</b></a></div><div class="navbar__items navbar__items--right"><a href="https://github.com/hzfe/awesome-interview" target="_blank" rel="noopener noreferrer" class="navbar__item navbar__link"><span>GitHub<svg width="13.5" height="13.5" aria-hidden="true" viewBox="0 0 24 24" class="iconExternalLink_3J9K"><path fill="currentColor" d="M21 13v10h-21v-19h12v2h-10v15h17v-8h2zm3-12h-10.988l4.035 4-6.977 7.07 2.828 2.828 6.977-7.07 4.125 4.172v-11z"></path></svg></span></a></div></div><div role="presentation" class="navbar-sidebar__backdrop"></div></nav><div class="main-wrapper docs-wrapper docs-doc-page"><div class="docPage_31aa"><button class="clean-btn backToTopButton_35hR" type="button"><svg viewBox="0 0 24 24" width="28"><path d="M7.41 15.41L12 10.83l4.59 4.58L18 14l-6-6-6 6z" fill="currentColor"></path></svg></button><aside class="docSidebarContainer_3Kbt"><div class="sidebar_15mo"><nav class="menu thin-scrollbar menu_Bmed menuWithAnnouncementBar_2WvA"><ul class="menu__list"><li class="menu__list-item"><a class="menu__link" href="/awesome-interview/">前言</a></li><li class="menu__list-item menu__list-item--collapsed"><a class="menu__link menu__link--sublist" href="#">模拟题一</a></li><li class="menu__list-item"><a class="menu__link menu__link--sublist menu__link--active" href="#">模拟题二</a><ul style="display:block;overflow:visible;height:auto" class="menu__list"><li class="menu__list-item"><a class="menu__link" tabindex="0" href="/awesome-interview/book2/browser-render-mechanism">浏览器：浏览器渲染机制</a></li><li class="menu__list-item"><a class="menu__link" tabindex="0" href="/awesome-interview/book2/browser-garbage">浏览器：垃圾回收机制</a></li><li class="menu__list-item"><a class="menu__link" tabindex="0" href="/awesome-interview/book2/engineer-babel">工程化：Babel 的原理</a></li><li class="menu__list-item"><a class="menu__link menu__link--active" aria-current="page" tabindex="0" href="/awesome-interview/book2/frame-react-fiber">框架：React Fiber 的作用和原理</a></li><li class="menu__list-item"><a class="menu__link" tabindex="0" href="/awesome-interview/book2/frame-react-hoc-hooks">框架：HOC vs Render Props vs Hooks</a></li><li class="menu__list-item"><a class="menu__link" tabindex="0" href="/awesome-interview/book2/js-inherite">基础：ES5、ES6 如何实现继承</a></li><li class="menu__list-item"><a class="menu__link" tabindex="0" href="/awesome-interview/book2/js-new">基础：New 操作符的原理</a></li><li class="menu__list-item"><a class="menu__link" tabindex="0" href="/awesome-interview/book2/css-preprocessor">样式：谈谈 CSS 预处理器</a></li><li class="menu__list-item"><a class="menu__link" tabindex="0" href="/awesome-interview/book2/network-http-cache">网络：HTTP 缓存机制</a></li><li class="menu__list-item"><a class="menu__link" tabindex="0" href="/awesome-interview/book2/coding-throttle-debounce">编码：实现节流去抖函数</a></li><li class="menu__list-item"><a class="menu__link" tabindex="0" href="/awesome-interview/book2/algorithm-reverse-linked-list">算法：反转链表</a></li><li class="menu__list-item"><a class="menu__link" tabindex="0" href="/awesome-interview/book2/topic-multi-pics-site-optimize">综合：多图站点性能优化</a
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由于 Fiber 采用了全新的调度方式，任务的更新过程可能会被打断，这意味着在组件更新过程中，render 及其之前的生命周期函数可能会调用多次。因此，在下列生命周期函数中不应出现副作用。</p><ul><li>shouldComponentUpdate</li><li>React 16 中已经声明废弃的钩子<ul><li>componentWillMount（UNSAFE_componentWillMount）</li><li>componentWillReceiveProps（UNSAFE_componentWillReceiveProps）</li><li>componentWillUpdate（UNSAFE_componentWillUpdate）</li></ul></li></ul><h2><a aria-hidden="true" tabindex="-1" class="anchor anchor__h2 anchorWithStickyNavbar_31ik" id="知识点深入"></a>知识点深入<a class="hash-link" href="#知识点深入" title="Direct link to heading">#</a></h2><h3><a aria-hidden="true" tabindex="-1" class="anchor anchor__h3 anchorWithStickyNavbar_31ik" id="1-react-是如何工作的"></a>1. React 是如何工作的<a class="hash-link" href="#1-react-是如何工作的" title="Direct link to heading">#</a></h3><div class="codeBlockContainer_K1bP"><div class="codeBlockContent_hGly jsx"><pre tabindex="0" class="prism-code language-jsx codeBlock_23N8 thin-scrollbar" style="color:#393A34;background-color:#f6f8fa"><code class="codeBlockLines_39YC"><span class="token-line" style="color:#393A34"><span class="token keyword" style="color:#00009f">import</span><span class="token plain"> React </span><span class="token keyword" style="color:#00009f">from</span><span class="token plain"> </span><span class="token string" style="color:#e3116c">"react"</span><span class="token punctuation" style="color:#393A34">;</span><span class="token plain"></span></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token keyword" style="color:#00009f">import</span><span class="token plain"> ReactDOM </span><span class="token keyword" style="color:#00009f">from</span><span class="token plain"> </span><span class="token string" style="color:#e3116c">"react-dom"</span><span class="token punctuation" style="color:#393A34">;</span><span class="token plain"></span></span><span class="token-line" style="color:#393A34"><span class="token plain" style="display:inline-block">
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</span></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token keyword" style="color:#00009f">function</span><span class="token plain"> </span><span class="token function" style="color:#d73a49">App</span><span class="token punctuation" style="color:#393A34">(</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">{</span><span class="token plain"></span></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token keyword" style="color:#00009f">return</span><span class="token plain"> </span><span class="token tag punctuation" style="color:#393A34"><</span><span class="token tag" style="color:#00009f">div</span><span class="token tag punctuation" style="color:#393A34">></span><span class="token plain">Hello</span><span class="token punctuation" style="color:#393A34">,</span><span class="token plain"> </span><span class="token constant" style="color:#36acaa">HZFE</span><span class="token punctuation" style="color:#393A34">.</span><span class="token tag punctuation" style="color:#393A34"></</span><span class="token tag" style="color:#00009f">div</span><span class="token tag punctuation" style="color:#393A34">></span><span class="token punctuation" style="color:#393A34">;</span><span class="token plain"></span></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token punctuation" style="color:#393A34">}</span><span class="token plain"></span></span><span class="token-line" style="color:#393A34"><span class="token plain" style="display:inline-block">
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</span></span><span class="token-line" style="color:#393A34"><span class="token plain">ReactDOM</span><span class="token punctuation" style="color:#393A34">.</span><span class="token function" style="color:#d73a49">render</span><span class="token punctuation" style="color:#393A34">(</span><span class="token tag punctuation" style="color:#393A34"><</span><span class="token tag class-name" style="color:#00009f">App</span><span class="token tag" style="color:#00009f"> </span><span class="token tag punctuation" style="color:#393A34">/></span><span class="token punctuation" style="color:#393A34">,</span><span class="token plain"> document</span><span class="token punctuation" style="color:#393A34">.</span><span class="token function" style="color:#d73a49">getElementById</span><span class="token punctuation" style="color:#393A34">(</span><span class="token string" style="color:#e3116c">"root"</span><span class="token punctuation" style="color:#393A34">)</span><span class="token punctuation" style="color:#393A34">)</span><span class="token punctuation" style="color:#393A34">;</span></span></code></pre><button type="button" aria-label="Copy code to clipboard" class="copyButton_Ue-o clean-btn">Copy</button></div></div><p>上面代码中我们引入的两个包，分别代表了 React 的 core API 层和渲染层，在这背后还有一层被称为协调器（Reconcilers）的层次。（协调器在<a href="https://github.com/facebook/react/tree/main/packages/react-reconciler" target="_blank" rel="noopener noreferrer">react-reconciler</a>中实现）</p><p>一个 React 组件的渲染主要经历两个阶段：</p><ul><li>调度阶段（Reconciler）：用新的数据生成一棵新的树，然后通过 Diff 算法，遍历旧的树，快速找出需要更新的元素，放到更新队列中去，得到新的更新队列。</li><li>渲染阶段（Renderer）：遍历更新队列，通过调用宿主环境的 API，实际更新渲染对应的元素。宿主环境如 DOM，Native 等。</li></ul><p>对于调度阶段，新老架构中有不同的处理方式：</p><p>React 16 之前使用的是 Stack Reconciler（栈协调器），使用递归的方式创建虚拟 DOM，递归的过程是不能中断的。如果组件树的层级很深，递归更新组件的时间超过 16ms，用户交互就会感觉到卡顿。</p><p><img src="https://user-images.githubusercontent.com/4338052/127518991-bea34058-35fc-4712-94d7-a3fc8df21df4.png" alt="image"></p><blockquote><p>图片来源 <a href="https://www.youtube.com/watch?v=5Wd5rxT7e1U&list=PLb0IAmt7-GS3fZ46IGFirdqKTIxlws7e0&index=4" target="_blank" rel="noopener noreferrer">react conf 17</a></p></blockquote><p>React 16 及以后使用的是 Fiber Reconciler（纤维协调器），将递归中无法中断的更新重构为迭代中的异步可中断更新过程，这样就能够更好的控制组件的渲染。</p><p><img src="https://user-images.githubusercontent.com/4338052/127519057-56e3a47a-19b4-42b0-9ad6-02b543c633cc.png" alt="image"></p><blockquote><p>图片来源 <a href="https://www.youtube.com/watch?v=5Wd5rxT7e1U&list=PLb0IAmt7-GS3fZ46IGFirdqKTIxlws7e0&index=4" target="_blank" rel="noopener noreferrer">react conf 17</a></p></blockquote><h3><a aria-hidden="true" tabindex="-1" class="anchor anchor__h3 anchorWithStickyNavbar_31ik" id="2-fiber-reconciler-如何工作"></a>2. Fiber Reconciler 如何工作<a class="hash-link" href="#2-fiber-reconciler-如何工作" title="Direct link to heading">#</a></h3><p>由于浏览器中 JS 的运行环境是单线程的，因此，一旦有任务耗时过长，就会阻塞其他任务的执行，导致浏览器不能及时响应用户的操作，从而使用户体验下降。为解决这个问题，React 推出了 Fiber Reconciler 架构。</p><p>在 Fiber 中，会把一个耗时很长的任务分成很多小的任务片，每一个任务片的运行时间很短。虽然总的任务执行时间依然很长，但是在每个任务小片执行完之后，都会给其他任务一个执行机会。
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这样，唯一的线程就不会被独占，其他任务也能够得到执行机会。</p><p>为了实现渐进渲染的目的，Fiber 架构中引入了新的数据结构：Fiber Node，Fiber Node Tree 根据 React Element Tree 生成，并用来驱动真实 DOM 的渲染。</p><p>Fiber 节点的大致结构：</p><div class="codeBlockContainer_K1bP"><div class="codeBlockContent_hGly js"><pre tabindex="0" class="prism-code language-js codeBlock_23N8 thin-scrollbar" style="color:#393A34;background-color:#f6f8fa"><code class="codeBlockLines_39YC"><span class="token-line" style="color:#393A34"><span class="token punctuation" style="color:#393A34">{</span><span class="token plain"></span></span><span class="token-line" style="color:#393A34"><span class="token plain"> tag</span><span class="token operator" style="color:#393A34">:</span><span class="token plain"> </span><span class="token maybe-class-name">TypeOfWork</span><span class="token punctuation" style="color:#393A34">,</span><span class="token plain"> </span><span class="token comment" style="color:#999988;font-style:italic">// 标识 fiber 类型</span><span class="token plain"></span></span><span class="token-line" style="color:#393A34"><span class="token plain"> type</span><span class="token operator" style="color:#393A34">:</span><span class="token plain"> </span><span class="token string" style="color:#e3116c">'div'</span><span class="token punctuation" style="color:#393A34">,</span><span class="token plain"> </span><span class="token comment" style="color:#999988;font-style:italic">// 和 fiber 相关的组件类型</span><span class="token plain"></span></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token keyword control-flow" style="color:#00009f">return</span><span class="token operator" style="color:#393A34">:</span><span class="token plain"> </span><span class="token maybe-class-name">Fiber</span><span class="token plain"> </span><span class="token operator" style="color:#393A34">|</span><span class="token plain"> </span><span class="token keyword null nil" style="color:#00009f">null</span><span class="token punctuation" style="color:#393A34">,</span><span class="token plain"> </span><span class="token comment" style="color:#999988;font-style:italic">// 父节点</span><span class="token plain"></span></span><span class="token-line" style="color:#393A34"><span class="token plain"> child</span><span class="token operator" style="color:#393A34">:</span><span class="token plain"> </span><span class="token maybe-class-name">Fiber</span><span class="token plain"> </span><span class="token operator" style="color:#393A34">|</span><span class="token plain"> </span><span class="token keyword null nil" style="color:#00009f">null</span><span class="token punctuation" style="color:#393A34">,</span><span class="token plain"> </span><span class="token comment" style="color:#999988;font-style:italic">// 子节点</span><span class="token plain"></span></span><span class="token-line" style="color:#393A34"><span class="token plain"> sibling</span><span class="token operator" style="color:#393A34">:</span><span class="token plain"> </span><span class="token maybe-class-name">Fiber</span><span class="token plain"> </span><span class="token operator" style="color:#393A34">|</span><span class="token plain"> </span><span class="token keyword null nil" style="color:#00009f">null</span><span class="token punctuation" style="color:#393A34">,</span><span class="token plain"> </span><span class="token comment" style="color:#999988;font-style:italic">// 同级节点</span><span class="token plain"></span></span><span class="token-line" style="color:#393A34"><span class="token plain"> alternate</span><span class="token operator" style="color:#393A34">:</span><span class="token plain"> </span><span class="token maybe-class-name">Fiber</span><span class="token plain"> </span><span class="token operator" style="color:#393A34">|</span><span class="token plain"> </span><span class="token keyword null nil" s
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