-
Notifications
You must be signed in to change notification settings - Fork 176
/
Copy pathframe-react-fiber.html
24 lines (24 loc) · 32.4 KB
/
frame-react-fiber.html
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
<!doctype html>
<html lang="en" dir="ltr" class="docs-wrapper docs-doc-page docs-version-current plugin-docs plugin-id-default docs-doc-id-book2/frame-react-fiber">
<head>
<meta charset="UTF-8">
<meta name="generator" content="Docusaurus v2.3.1">
<title data-rh="true">React Fiber 的作用和原理 | HZFE - 剑指前端 Offer</title><meta data-rh="true" name="viewport" content="width=device-width,initial-scale=1"><meta data-rh="true" name="twitter:card" content="summary_large_image"><meta data-rh="true" property="og:url" content="https://febook.hzfe.org/awesome-interview/book2/frame-react-fiber"><meta data-rh="true" name="docusaurus_locale" content="en"><meta data-rh="true" name="docsearch:language" content="en"><meta data-rh="true" name="docusaurus_version" content="current"><meta data-rh="true" name="docusaurus_tag" content="docs-default-current"><meta data-rh="true" name="docsearch:version" content="current"><meta data-rh="true" name="docsearch:docusaurus_tag" content="docs-default-current"><meta data-rh="true" property="og:title" content="React Fiber 的作用和原理 | HZFE - 剑指前端 Offer"><meta data-rh="true" name="description" content="相关问题"><meta data-rh="true" property="og:description" content="相关问题"><link data-rh="true" rel="icon" href="/awesome-interview/img/favicon.ico"><link data-rh="true" rel="canonical" href="https://febook.hzfe.org/awesome-interview/book2/frame-react-fiber"><link data-rh="true" rel="alternate" href="https://febook.hzfe.org/awesome-interview/book2/frame-react-fiber" hreflang="en"><link data-rh="true" rel="alternate" href="https://febook.hzfe.org/awesome-interview/book2/frame-react-fiber" hreflang="x-default"><link data-rh="true" rel="preconnect" href="https://PED5MQGL7T-dsn.algolia.net" crossorigin="anonymous"><link rel="search" type="application/opensearchdescription+xml" title="HZFE - 剑指前端 Offer" href="/awesome-interview/opensearch.xml">
<link rel="apple-touch-icon" href="/awesome-interview/img/badge.png">
<link rel="manifest" href="/awesome-interview/manifest.json">
<link rel="preconnect" href="https://hm.baidu.com">
<script>var _hmt=_hmt||[];!function(){var e=document.createElement("script");e.src="https://hm.baidu.com/hm.js?c7cd0fd77ac518cc6ef46461cdc9524b";var c=document.getElementsByTagName("script")[0];c.parentNode.insertBefore(e,c)}()</script>
<script src="https://pagead2.googlesyndication.com/pagead/js/adsbygoogle.js" async data-ad-client="ca-pub-9889934432771967"></script>
<script src="https://pagead2.googlesyndication.com/pagead/js/adsbygoogle.js?client=ca-pub-9889934432771967" async crossorigin="anonymous"></script><link rel="stylesheet" href="/awesome-interview/assets/css/styles.0f62048e.css">
<link rel="preload" href="/awesome-interview/assets/js/runtime~main.a75952d5.js" as="script">
<link rel="preload" href="/awesome-interview/assets/js/main.a5e14537.js" as="script">
</head>
<body class="navigation-with-keyboard">
<script>!function(){function t(t){document.documentElement.setAttribute("data-theme",t)}var e=function(){var t=null;try{t=localStorage.getItem("theme")}catch(t){}return t}();t(null!==e?e:"light")}()</script><div id="__docusaurus">
<div role="region" aria-label="Skip to main content"><a class="skipToContent_fXgn" href="#docusaurus_skipToContent_fallback">Skip to main content</a></div><nav aria-label="Main" class="navbar navbar--fixed-top navbarHideable_m1mJ"><div class="navbar__inner"><div class="navbar__items"><button aria-label="Toggle navigation bar" aria-expanded="false" class="navbar__toggle clean-btn" type="button"><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/"><div class="navbar__logo"><img src="/awesome-interview/img/badge.svg" alt="HZFE" class="themedImage_ToTc themedImage--light_HNdA"><img src="/awesome-interview/img/badge.svg" alt="HZFE" class="themedImage_ToTc themedImage--dark_i4oU"></div><b class="navbar__title text--truncate">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">GitHub<svg width="13.5" height="13.5" aria-hidden="true" viewBox="0 0 24 24" class="iconExternalLink_nPIU"><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></a><div class="searchBox_ZlJk"><button type="button" class="DocSearch DocSearch-Button" aria-label="Search"><span class="DocSearch-Button-Container"><svg width="20" height="20" class="DocSearch-Search-Icon" viewBox="0 0 20 20"><path d="M14.386 14.386l4.0877 4.0877-4.0877-4.0877c-2.9418 2.9419-7.7115 2.9419-10.6533 0-2.9419-2.9418-2.9419-7.7115 0-10.6533 2.9418-2.9419 7.7115-2.9419 10.6533 0 2.9419 2.9418 2.9419 7.7115 0 10.6533z" stroke="currentColor" fill="none" fill-rule="evenodd" stroke-linecap="round" stroke-linejoin="round"></path></svg><span class="DocSearch-Button-Placeholder">Search</span></span><span class="DocSearch-Button-Keys"></span></button></div></div></div><div role="presentation" class="navbar-sidebar__backdrop"></div></nav><div id="docusaurus_skipToContent_fallback" class="main-wrapper mainWrapper_z2l0 docsWrapper_BCFX"><button aria-label="Scroll back to top" class="clean-btn theme-back-to-top-button backToTopButton_sjWU" type="button"></button><div class="docPage__5DB"><aside class="theme-doc-sidebar-container docSidebarContainer_b6E3"><div class="sidebarViewport_Xe31"><div class="sidebar_njMd sidebarWithHideableNavbar_wUlq"><a tabindex="-1" class="sidebarLogo_isFc" href="/awesome-interview/"><img src="/awesome-interview/img/badge.svg" alt="HZFE" class="themedImage_ToTc themedImage--light_HNdA"><img src="/awesome-interview/img/badge.svg" alt="HZFE" class="themedImage_ToTc themedImage--dark_i4oU"><b>剑指前端 Offer</b></a><nav aria-label="Docs sidebar" class="menu thin-scrollbar menu_SIkG"><ul class="theme-doc-sidebar-menu menu__list"><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-1 menu__list-item"><a class="menu__link" href="/awesome-interview/about">关于我们</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-1 menu__list-item"><a class="menu__link" href="/awesome-interview/">前言</a></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="/awesome-interview/book1/browser-cross-origin">模拟题一</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret menu__link--active" aria-expanded="true" href="/awesome-interview/book2/browser-render-mechanism">模拟题二</a></div><ul style="display:block;overflow:visible;height:auto" class="menu__list"><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 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="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 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="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 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="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 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="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 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="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 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="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 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="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 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="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 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="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item"><a class="menu__link" tabindex="0" href="/awesome-interview/book2/coding-throttle-debounce">编码：实现节流防抖函数</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 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="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 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></li></ul></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="/awesome-interview/book3/browser-event-loop">模拟题三</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="/awesome-interview/book4/browser-router">模拟题四</a></div></li></ul></nav><button type="button" title="Collapse sidebar" aria-label="Collapse sidebar" class="button button--secondary button--outline collapseSidebarButton_PEFL"><svg width="20" height="20" aria-hidden="true" class="collapseSidebarButtonIcon_kv0_"><g fill="#7a7a7a"><path d="M9.992 10.023c0 .2-.062.399-.172.547l-4.996 7.492a.982.982 0 01-.828.454H1c-.55 0-1-.453-1-1 0-.2.059-.403.168-.551l4.629-6.942L.168 3.078A.939.939 0 010 2.528c0-.548.45-.997 1-.997h2.996c.352 0 .649.18.828.45L9.82 9.472c.11.148.172.347.172.55zm0 0"></path><path d="M19.98 10.023c0 .2-.058.399-.168.547l-4.996 7.492a.987.987 0 01-.828.454h-3c-.547 0-.996-.453-.996-1 0-.2.059-.403.168-.551l4.625-6.942-4.625-6.945a.939.939 0 01-.168-.55 1 1 0 01.996-.997h3c.348 0 .649.18.828.45l4.996 7.492c.11.148.168.347.168.55zm0 0"></path></g></svg></button></div></div></aside><main class="docMainContainer_gTbr"><div class="container padding-top--md padding-bottom--lg"><div class="row"><div class="col docItemCol_VOVn"><div class="docItemContainer_Djhp"><article><nav class="theme-doc-breadcrumbs breadcrumbsContainer_Z_bl" aria-label="Breadcrumbs"><ul class="breadcrumbs" itemscope="" itemtype="https://schema.org/BreadcrumbList"><li class="breadcrumbs__item"><a aria-label="Home page" class="breadcrumbs__link" href="/awesome-interview/"><svg viewBox="0 0 24 24" class="breadcrumbHomeIcon_YNFT"><path d="M10 19v-5h4v5c0 .55.45 1 1 1h3c.55 0 1-.45 1-1v-7h1.7c.46 0 .68-.57.33-.87L12.67 3.6c-.38-.34-.96-.34-1.34 0l-8.36 7.53c-.34.3-.13.87.33.87H5v7c0 .55.45 1 1 1h3c.55 0 1-.45 1-1z" fill="currentColor"></path></svg></a></li><li class="breadcrumbs__item"><span class="breadcrumbs__link">模拟题二</span><meta itemprop="position" content="1"></li><li itemscope="" itemprop="itemListElement" itemtype="https://schema.org/ListItem" class="breadcrumbs__item breadcrumbs__item--active"><span class="breadcrumbs__link" itemprop="name">框架：React Fiber 的作用和原理</span><meta itemprop="position" content="2"></li></ul></nav><div class="tocCollapsible_ETCw theme-doc-toc-mobile tocMobile_ITEo"><button type="button" class="clean-btn tocCollapsibleButton_TO0P">On this page</button></div><div class="theme-doc-markdown markdown"><h1>React Fiber 的作用和原理</h1><h2 class="anchor anchorWithHideOnScrollNavbar_WYt5" id="相关问题">相关问题<a href="#相关问题" class="hash-link" aria-label="Direct link to 相关问题" title="Direct link to 相关问题"></a></h2><ul><li>Fiber 是什么</li><li>谈谈你对 Fiber 的了解</li><li>Fiber 对 React 的使用带来了什么影响</li></ul><h2 class="anchor anchorWithHideOnScrollNavbar_WYt5" id="回答关键点">回答关键点<a href="#回答关键点" class="hash-link" aria-label="Direct link to 回答关键点" title="Direct link to 回答关键点"></a></h2><p><code>调度</code> <code>深度优先遍历</code></p><p>Fiber 是 React 16 中采用的新协调（reconciliation）引擎，主要目标是支持虚拟 DOM 的渐进式渲染。</p><p>Fiber 将原有的 Stack Reconciler 替换为 Fiber Reconciler，提高了复杂应用的可响应性和性能。主要通过以下方式达成目标：</p><ul><li>对大型复杂任务的分片。</li><li>对任务划分优先级，优先调度高优先级的任务。</li><li>调度过程中，可以对任务进行挂起、恢复、终止等操作。</li></ul><p>Fiber 对现有代码的影响：
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 class="anchor anchorWithHideOnScrollNavbar_WYt5" id="知识点深入">知识点深入<a href="#知识点深入" class="hash-link" aria-label="Direct link to 知识点深入" title="Direct link to 知识点深入"></a></h2><h3 class="anchor anchorWithHideOnScrollNavbar_WYt5" id="1-react-是如何工作的">1. React 是如何工作的<a href="#1-react-是如何工作的" class="hash-link" aria-label="Direct link to 1. React 是如何工作的" title="Direct link to 1. React 是如何工作的"></a></h3><div class="language-jsx codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#393A34;--prism-background-color:#f6f8fa"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-jsx codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#393A34"><span class="token keyword module" style="color:#00009f">import</span><span class="token plain"> </span><span class="token imports maybe-class-name">React</span><span class="token plain"> </span><span class="token keyword module" 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><br></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token keyword module" style="color:#00009f">import</span><span class="token plain"> </span><span class="token imports maybe-class-name">ReactDOM</span><span class="token plain"> </span><span class="token keyword module" 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><br></span><span class="token-line" style="color:#393A34"><span class="token plain" style="display:inline-block"></span><br></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 maybe-class-name" 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><br></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 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-text">Hello, HZFE.</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><br></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><br></span><span class="token-line" style="color:#393A34"><span class="token plain" style="display:inline-block"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token maybe-class-name">ReactDOM</span><span class="token punctuation" style="color:#393A34">.</span><span class="token method function property-access" 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"> </span><span class="token dom variable" style="color:#36acaa">document</span><span class="token punctuation" style="color:#393A34">.</span><span class="token method function property-access" 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><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg class="copyButtonIcon_y97N" viewBox="0 0 24 24"><path d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg class="copyButtonSuccessIcon_LjdS" viewBox="0 0 24 24"><path d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></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（以 60Hz 频率的显示器为例，浏览器绘制一帧的最小时间间隔为 1/60s 约等于 16ms），这时会发生俗称的掉帧现象，帧率不稳定时，用户就会感觉到卡顿。</p><p><img loading="lazy" src="https://user-images.githubusercontent.com/4338052/127518991-bea34058-35fc-4712-94d7-a3fc8df21df4.png" alt="image" class="img_ev3q"></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 loading="lazy" src="https://user-images.githubusercontent.com/4338052/127519057-56e3a47a-19b4-42b0-9ad6-02b543c633cc.png" alt="image" class="img_ev3q"></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 class="anchor anchorWithHideOnScrollNavbar_WYt5" id="2-fiber-reconciler-如何工作">2. Fiber Reconciler 如何工作<a href="#2-fiber-reconciler-如何工作" class="hash-link" aria-label="Direct link to 2. Fiber Reconciler 如何工作" title="Direct link to 2. Fiber Reconciler 如何工作"></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。
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="language-js codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#393A34;--prism-background-color:#f6f8fa"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-js codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#393A34"><span class="token punctuation" style="color:#393A34">{</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token literal-property property" style="color:#36acaa">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><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token literal-property property" style="color:#36acaa">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><br></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><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token literal-property property" style="color:#36acaa">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><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token literal-property property" style="color:#36acaa">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><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token literal-property property" style="color:#36acaa">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" 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">// diff 的变化记录在这个节点上</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token spread operator" style="color:#393A34">...</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token punctuation" style="color:#393A34">}</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg class="copyButtonIcon_y97N" viewBox="0 0 24 24"><path d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg class="copyButtonSuccessIcon_LjdS" viewBox="0 0 24 24"><path d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div><p>Fiber 树结构如下：</p><p><img loading="lazy" src="https://user-images.githubusercontent.com/11912260/44942438-4c0e7f00-ade3-11e8-83ea-161e2aedcf8e.png" alt="Fiber Tree" class="img_ev3q"></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>Fiber 的主要工作流程：</p><ol><li><code>ReactDOM.render()</code> 引导 React 启动或调用 <code>setState()</code> 的时候开始创建或更新 Fiber 树。</li><li>从根节点开始遍历 Fiber Node Tree， 并且构建 workInProgress Tree（reconciliation 阶段）。<ul><li>本阶段可以暂停、终止、和重启，会导致 react 相关生命周期重复执行。</li><li>React 会生成两棵树，一棵是代表当前状态的 current tree，一棵是待更新的 workInProgress tree。</li><li>遍历 current tree，重用或更新 Fiber Node 到 workInProgress tree，workInProgress tree 完成后会替换 current tree。</li><li>每更新一个节点，同时生成该节点对应的 Effect List。</li><li>为每个节点创建更新任务。</li></ul></li><li>将创建的更新任务加入任务队列，等待调度。<ul><li>调度由 scheduler 模块完成，其核心职责是执行回调。</li><li>scheduler 模块实现了跨平台兼容的 requestIdleCallback。</li><li>每处理完一个 Fiber Node 的更新，可以中断、挂起，或恢复。</li></ul></li><li>根据 Effect List 更新 DOM （commit 阶段）。<ul><li>React 会遍历 Effect List 将所有变更一次性更新到 DOM 上。</li><li>这一阶段的工作会导致用户可见的变化。因此该过程不可中断，必须一直执行直到更新完成。</li></ul></li></ol><p>React 调度流程图：</p><p><img loading="lazy" src="https://user-images.githubusercontent.com/4338052/127530996-23513132-f3ef-4a3e-8553-8bfef2e3669b.png" alt="image" class="img_ev3q"></p><h2 class="anchor anchorWithHideOnScrollNavbar_WYt5" id="参考资料">参考资料<a href="#参考资料" class="hash-link" aria-label="Direct link to 参考资料" title="Direct link to 参考资料"></a></h2><ol><li><a href="https://github.com/acdlite/react-fiber-architecture" target="_blank" rel="noopener noreferrer">React Fiber Architecture</a></li><li><a href="https://www.youtube.com/watch?v=7HSd1sk07uU&list=PLb0IAmt7-GS3fZ46IGFirdqKTIxlws7e0" target="_blank" rel="noopener noreferrer">React Conf 2017</a></li><li><a href="https://blog.ag-grid.com/inside-fiber-an-in-depth-overview-of-the-new-reconciliation-algorithm-in-react/" target="_blank" rel="noopener noreferrer">Inside Fiber</a></li></ol></div></article><nav class="pagination-nav docusaurus-mt-lg" aria-label="Docs pages navigation"><a class="pagination-nav__link pagination-nav__link--prev" href="/awesome-interview/book2/engineer-babel"><div class="pagination-nav__sublabel">Previous</div><div class="pagination-nav__label">工程化：Babel 的原理</div></a><a class="pagination-nav__link pagination-nav__link--next" href="/awesome-interview/book2/frame-react-hoc-hooks"><div class="pagination-nav__sublabel">Next</div><div class="pagination-nav__label">框架：HOC vs Render Props vs Hooks</div></a></nav></div></div><div class="col col--3"><div class="tableOfContents_bqdL thin-scrollbar theme-doc-toc-desktop"><ul class="table-of-contents table-of-contents__left-border"><li><a href="#相关问题" class="table-of-contents__link toc-highlight">相关问题</a></li><li><a href="#回答关键点" class="table-of-contents__link toc-highlight">回答关键点</a></li><li><a href="#知识点深入" class="table-of-contents__link toc-highlight">知识点深入</a><ul><li><a href="#1-react-是如何工作的" class="table-of-contents__link toc-highlight">1. React 是如何工作的</a></li><li><a href="#2-fiber-reconciler-如何工作" class="table-of-contents__link toc-highlight">2. Fiber Reconciler 如何工作</a></li></ul></li><li><a href="#参考资料" class="table-of-contents__link toc-highlight">参考资料</a></li></ul></div></div></div><div class="row"><div class="col"><div class="react-utterences"><div>Loading script...</div></div></div><div class="col col--3"></div></div></div></main></div></div></div>
<script src="/awesome-interview/assets/js/runtime~main.a75952d5.js"></script>
<script src="/awesome-interview/assets/js/main.a5e14537.js"></script>
</body>
</html>