21 lines
45 KiB
HTML
21 lines
45 KiB
HTML
<!doctype html>
|
||
<html lang="en" dir="ltr" class="docs-wrapper docs-doc-page docs-version-current plugin-docs plugin-id-default docs-doc-id-book4/frame-react-event-mechanism">
|
||
<head>
|
||
<meta charset="UTF-8">
|
||
<meta name="viewport" content="width=device-width,initial-scale=1">
|
||
<meta name="generator" content="Docusaurus v2.0.0-beta.18">
|
||
<link rel="search" type="application/opensearchdescription+xml" title="HZFE - 剑指前端 Offer" href="/awesome-interview/opensearch.xml">
|
||
<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><title data-rh="true">React 事件机制原理 | HZFE - 剑指前端 Offer</title><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/book4/frame-react-event-mechanism"><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 事件机制原理 | 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/book4/frame-react-event-mechanism"><link data-rh="true" rel="alternate" href="https://febook.hzfe.org/awesome-interview/book4/frame-react-event-mechanism" hreflang="en"><link data-rh="true" rel="alternate" href="https://febook.hzfe.org/awesome-interview/book4/frame-react-event-mechanism" hreflang="x-default"><link data-rh="true" rel="preconnect" href="https://PED5MQGL7T-dsn.algolia.net" crossorigin="anonymous"><link rel="stylesheet" href="/awesome-interview/assets/css/styles.62902d4b.css">
|
||
<link rel="preload" href="/awesome-interview/assets/js/runtime~main.16895322.js" as="script">
|
||
<link rel="preload" href="/awesome-interview/assets/js/main.a6349f88.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"><a href="#" class="skipToContent_ZgBM">Skip to main content</a></div><nav class="navbar navbar--fixed-top navbarHideable_ObN2"><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/"><div class="navbar__logo"><img src="/awesome-interview/img/badge.svg" alt="HZFE" class="themedImage_W2Cr themedImage--light_TfLj"><img src="/awesome-interview/img/badge.svg" alt="HZFE" class="themedImage_W2Cr themedImage--dark_oUvU"></div><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">GitHub<svg width="13.5" height="13.5" aria-hidden="true" viewBox="0 0 24 24" class="iconExternalLink_I5OW"><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_qEbK"><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 class="main-wrapper"><div class="docPage_P2Lg"><button aria-label="Scroll back to top" class="clean-btn theme-back-to-top-button backToTopButton_RiI4" type="button"></button><aside class="theme-doc-sidebar-container docSidebarContainer_rKC_"><div class="sidebar_RiAD sidebarWithHideableNavbar_d0QC"><a tabindex="-1" class="sidebarLogo_YUvz" href="/awesome-interview/"><img src="/awesome-interview/img/badge.svg" alt="HZFE" class="themedImage_W2Cr themedImage--light_TfLj"><img src="/awesome-interview/img/badge.svg" alt="HZFE" class="themedImage_W2Cr themedImage--dark_oUvU"><b>剑指前端 Offer</b></a><nav class="menu thin-scrollbar menu_izAj"><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 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/book2/browser-render-mechanism">模拟题二</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/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"><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/book4/browser-router">模拟题四</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/book4/browser-router">浏览器：前端路由实现</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/book4/browser-local-storage">浏览器：本地存储方式及场景</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/book4/engineer-front-end-testing">工程化：如何对前端代码实施测试</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/book4/engineer-mfa">工程化：谈谈微前端</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/book4/frame-react-event-mechanism">框架：React 事件机制原理</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/book4/frame-react-vs-vue">框架：谈谈 React 和 Vue 的区别</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/book4/js-ts-generics">基础：什么是 TypeScript 泛型</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/book4/css-vertical-horizontal-center">样式：水平垂直居中方案</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/book4/coding-apply-call-bind">编码：实现 apply/call/bind</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/book4/array-repeat-number">算法：找到数组中重复的数字</a></li></ul></li></ul></nav><button type="button" title="Collapse sidebar" aria-label="Collapse sidebar" class="button button--secondary button--outline collapseSidebarButton_FykI"><svg width="20" height="20" aria-hidden="true" class="collapseSidebarButtonIcon_DTRl"><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></aside><main class="docMainContainer_TCnq"><div class="container padding-top--md padding-bottom--lg"><div class="row"><div class="col docItemCol_DM6M"><div class="docItemContainer_vinB"><article><nav class="theme-doc-breadcrumbs breadcrumbsContainer_Xlws" aria-label="breadcrumbs"><ul class="breadcrumbs" itemscope="" itemtype="https://schema.org/BreadcrumbList"><li class="breadcrumbs__item"><a class="breadcrumbs__link" href="/awesome-interview/">🏠</a></li><li itemscope="" itemprop="itemListElement" itemtype="https://schema.org/ListItem" class="breadcrumbs__item"><span class="breadcrumbs__link" itemprop="item name">模拟题四</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="item name">框架：React 事件机制原理</span><meta itemprop="position" content="2"></li></ul></nav><div class="tocCollapsible_jdIR theme-doc-toc-mobile tocMobile_TmEX"><button type="button" class="clean-btn tocCollapsibleButton_Fzxq">On this page</button></div><div class="theme-doc-markdown markdown"><h1>React 事件机制原理</h1><h2 class="anchor anchorWithHideOnScrollNavbar_R0VQ" id="相关问题">相关问题<a class="hash-link" href="#相关问题" title="Direct link to heading"></a></h2><ul><li>React 合成事件与原生 DOM 事件的区别</li><li>React 如何注册和触发事件</li><li>React 事件如何解决浏览器兼容问题</li></ul><h2 class="anchor anchorWithHideOnScrollNavbar_R0VQ" id="回答关键点">回答关键点<a class="hash-link" href="#回答关键点" title="Direct link to heading"></a></h2><p>React 的事件处理机制可以分为两个阶段：初始化渲染时在 root 节点上注册原生事件；原生事件触发时模拟捕获、目标和冒泡阶段派发合成事件。通过这种机制，冒泡的原生事件类型最多在 root 节点上注册一次，节省内存开销。且 React 为不同类型的事件定义了不同的处理优先级，从而让用户代码及时响应高优先级的用户交互，提升用户体验。</p><p>React 的事件机制中依赖合成事件这个核心概念。合成事件在符合 W3C 规范定义的前提下，抹平浏览器之间的差异化表现。并且简化事件逻辑，对关联事件进行合成。如每当表单类型组件的值发生改变时，都会触发 onChange 事件，而 onChange 事件由 change、click、input、keydown、keyup 等原生事件组成。</p><h2 class="anchor anchorWithHideOnScrollNavbar_R0VQ" id="知识点深入">知识点深入<a class="hash-link" href="#知识点深入" title="Direct link to heading"></a></h2><h3 class="anchor anchorWithHideOnScrollNavbar_R0VQ" id="1-原生事件和合成事件">1. 原生事件和合成事件<a class="hash-link" href="#1-原生事件和合成事件" title="Direct link to heading"></a></h3><p>JavaScript 通过事件可以和 DOM 进行交互。</p><h4 class="anchor anchorWithHideOnScrollNavbar_R0VQ" id="11-原生事件">1.1 原生事件<a class="hash-link" href="#11-原生事件" title="Direct link to heading"></a></h4><p>主流浏览器基于 DOM2、DOM3 规范，实现标准化 DOM 事件。基于 Event 实现了浏览器中常见的用户事件如 UIEvent、InputEvent、MouseEvent 等。</p><p>在事件发生时，相关信息会存储在 Event 的实例对象中，对象包含 currentTarget、detail、target、preventDefault()、stopPropagation() 等属性和方法。DOM 节点可以通过 addEventListener 和 removeEventListener 来添加或移除事件监听函数。</p><div class="codeBlockContainer_I0IT language-ts theme-code-block"><div class="codeBlockContent_wNvx" style="color:#393A34;background-color:#f6f8fa"><pre tabindex="0" class="prism-code language-ts codeBlock_jd64 thin-scrollbar"><code class="codeBlockLines_mRuA"><span class="token-line" style="color:#393A34"><span class="token comment" style="color:#999988;font-style:italic">// Event 属性</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token builtin">boolean</span><span class="token plain"> bubbles</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token builtin">boolean</span><span class="token plain"> cancelable</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token maybe-class-name">DOMEventTarget</span><span class="token plain"> currentTarget</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token builtin">boolean</span><span class="token plain"> defaultPrevented</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token builtin">number</span><span class="token plain"> eventPhase</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token builtin">boolean</span><span class="token plain"> isTrusted</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token keyword" style="color:#00009f">void</span><span class="token plain"> </span><span class="token function" style="color:#d73a49">preventDefault</span><span class="token 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 keyword" style="color:#00009f">void</span><span class="token plain"> </span><span class="token function" style="color:#d73a49">stopPropagation</span><span class="token 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 keyword" style="color:#00009f">void</span><span class="token plain"> </span><span class="token function" style="color:#d73a49">stopImmediatePropagation</span><span class="token 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 maybe-class-name">DOMEventTarget</span><span class="token plain"> target</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token builtin">number</span><span class="token plain"> timeStamp</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token builtin">string</span><span class="token plain"> </span><span class="token keyword" style="color:#00009f">type</span><br></span></code></pre><button type="button" aria-label="Copy code to clipboard" title="Copy" class="copyButton_eDfN clean-btn"><span class="copyButtonIcons_W9eQ" aria-hidden="true"><svg class="copyButtonIcon_XEyF" 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_i9w9" 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><h4 class="anchor anchorWithHideOnScrollNavbar_R0VQ" id="12-react-合成事件">1.2 React 合成事件<a class="hash-link" href="#12-react-合成事件" title="Direct link to heading"></a></h4><p>React 的事件机制中，在遵循规范的前提下，引入新的事件类型：合成事件（SyntheticEvent）。基于合成事件实现了浏览器中常见的用户事件，并对事件进行规范化处理，使它们在不同浏览器中具有一致的属性。</p><p>在事件发生时，相关信息会存储在 SyntheticEvent 的实例对象中，对象包含原生事件对象类似的属性。</p><div class="codeBlockContainer_I0IT language-ts theme-code-block"><div class="codeBlockContent_wNvx" style="color:#393A34;background-color:#f6f8fa"><pre tabindex="0" class="prism-code language-ts codeBlock_jd64 thin-scrollbar"><code class="codeBlockLines_mRuA"><span class="token-line" style="color:#393A34"><span class="token comment" style="color:#999988;font-style:italic">// SyntheticEvent 属性</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token builtin">boolean</span><span class="token plain"> bubbles</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token builtin">boolean</span><span class="token plain"> cancelable</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token maybe-class-name">DOMEventTarget</span><span class="token plain"> currentTarget</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token builtin">boolean</span><span class="token plain"> defaultPrevented</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token builtin">number</span><span class="token plain"> eventPhase</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token builtin">boolean</span><span class="token plain"> isTrusted</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token maybe-class-name">DOMEvent</span><span class="token plain"> nativeEvent</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token keyword" style="color:#00009f">void</span><span class="token plain"> </span><span class="token function" style="color:#d73a49">preventDefault</span><span class="token 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 builtin">boolean</span><span class="token plain"> </span><span class="token function" style="color:#d73a49">isDefaultPrevented</span><span class="token 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 keyword" style="color:#00009f">void</span><span class="token plain"> </span><span class="token function" style="color:#d73a49">stopPropagation</span><span class="token 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 builtin">boolean</span><span class="token plain"> </span><span class="token function" style="color:#d73a49">isPropagationStopped</span><span class="token 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 keyword" style="color:#00009f">void</span><span class="token plain"> </span><span class="token function" style="color:#d73a49">persist</span><span class="token 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 maybe-class-name">DOMEventTarget</span><span class="token plain"> target</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token builtin">number</span><span class="token plain"> timeStamp</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token builtin">string</span><span class="token plain"> </span><span class="token keyword" style="color:#00009f">type</span><br></span></code></pre><button type="button" aria-label="Copy code to clipboard" title="Copy" class="copyButton_eDfN clean-btn"><span class="copyButtonIcons_W9eQ" aria-hidden="true"><svg class="copyButtonIcon_XEyF" 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_i9w9" 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><p>但是合成事件与原生事件不是一一映射的关系。比如 onMouseEnter 合成事件映射原生 mouseout、mouseover 事件。React 通过 registrationNameDependencies 来记录合成事件和原生事件的映射关系：</p><div class="codeBlockContainer_I0IT language-js theme-code-block"><div class="codeBlockContent_wNvx" style="color:#393A34;background-color:#f6f8fa"><pre tabindex="0" class="prism-code language-js codeBlock_jd64 thin-scrollbar"><code class="codeBlockLines_mRuA"><span class="token-line" style="color:#393A34"><span class="token comment" style="color:#999988;font-style:italic">/**</span><br></span><span class="token-line" style="color:#393A34"><span class="token comment" style="color:#999988;font-style:italic"> * Mapping from registration name to event name</span><br></span><span class="token-line" style="color:#393A34"><span class="token comment" style="color:#999988;font-style:italic"> */</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">export</span><span class="token plain"> </span><span class="token keyword" style="color:#00009f">const</span><span class="token plain"> registrationNameDependencies </span><span class="token operator" 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 literal-property property" style="color:#36acaa">onClick</span><span class="token operator" style="color:#393A34">:</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">[</span><span class="token string" style="color:#e3116c">"click"</span><span class="token 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 literal-property property" style="color:#36acaa">onMouseEnter</span><span class="token operator" style="color:#393A34">:</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">[</span><span class="token string" style="color:#e3116c">"mouseout"</span><span class="token punctuation" style="color:#393A34">,</span><span class="token plain"> </span><span class="token string" style="color:#e3116c">"mouseover"</span><span class="token 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 literal-property property" style="color:#36acaa">onChange</span><span class="token operator" 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 string" style="color:#e3116c">"change"</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 string" style="color:#e3116c">"click"</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 string" style="color:#e3116c">"focusin"</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 string" style="color:#e3116c">"focusout"</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 string" style="color:#e3116c">"input"</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 string" style="color:#e3116c">"keydown"</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 string" style="color:#e3116c">"keyup"</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 string" style="color:#e3116c">"selectionchange"</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 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 comment" style="color:#999988;font-style:italic">// ...</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 punctuation" style="color:#393A34">;</span><br></span></code></pre><button type="button" aria-label="Copy code to clipboard" title="Copy" class="copyButton_eDfN clean-btn"><span class="copyButtonIcons_W9eQ" aria-hidden="true"><svg class="copyButtonIcon_XEyF" 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_i9w9" 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><h3 class="anchor anchorWithHideOnScrollNavbar_R0VQ" id="2-react-事件机制">2. React 事件机制<a class="hash-link" href="#2-react-事件机制" title="Direct link to heading"></a></h3><h4 class="anchor anchorWithHideOnScrollNavbar_R0VQ" id="21-react-事件的注册">2.1 React 事件的注册<a class="hash-link" href="#21-react-事件的注册" title="Direct link to heading"></a></h4><p><img loading="lazy" src="https://user-images.githubusercontent.com/17002181/143735223-cb577bcf-8e4c-4047-8818-cbc28a1e8b69.png" class="img_E7b_"></p><p>使用 ReactDOM.createRoot 创建 Root 时，React 会调用 listenToAllSupportedEvents 方法对所有支持的原生事件进行监听：</p><ol><li>allNativeEvents 用于收集所有合成事件相关联的原生事件名。这个收集动作在事件插件初始化阶段完成；</li></ol><div class="codeBlockContainer_I0IT language-js theme-code-block"><div class="codeBlockContent_wNvx" style="color:#393A34;background-color:#f6f8fa"><pre tabindex="0" class="prism-code language-js codeBlock_jd64 thin-scrollbar"><code class="codeBlockLines_mRuA"><span class="token-line" style="color:#393A34"><span class="token maybe-class-name">SimpleEventPlugin</span><span class="token punctuation" style="color:#393A34">.</span><span class="token method function property-access" style="color:#d73a49">registerEvents</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 class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token maybe-class-name">EnterLeaveEventPlugin</span><span class="token punctuation" style="color:#393A34">.</span><span class="token method function property-access" style="color:#d73a49">registerEvents</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 class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token maybe-class-name">ChangeEventPlugin</span><span class="token punctuation" style="color:#393A34">.</span><span class="token method function property-access" style="color:#d73a49">registerEvents</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 class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token maybe-class-name">SelectEventPlugin</span><span class="token punctuation" style="color:#393A34">.</span><span class="token method function property-access" style="color:#d73a49">registerEvents</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 class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token maybe-class-name">BeforeInputEventPlugin</span><span class="token punctuation" style="color:#393A34">.</span><span class="token method function property-access" style="color:#d73a49">registerEvents</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><button type="button" aria-label="Copy code to clipboard" title="Copy" class="copyButton_eDfN clean-btn"><span class="copyButtonIcons_W9eQ" aria-hidden="true"><svg class="copyButtonIcon_XEyF" 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_i9w9" 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><ol start="2"><li>对每个原生事件调用 addTrappedEventListener 函数。该函数最终使用 addEventListener 方法，对原生事件进行捕获或冒泡阶段的事件监听注册。</li></ol><div class="codeBlockContainer_I0IT language-ts theme-code-block"><div class="codeBlockContent_wNvx" style="color:#393A34;background-color:#f6f8fa"><pre tabindex="0" class="prism-code language-ts codeBlock_jd64 thin-scrollbar"><code class="codeBlockLines_mRuA"><span class="token-line" style="color:#393A34"><span class="token keyword" style="color:#00009f">function</span><span class="token plain"> </span><span class="token function" style="color:#d73a49">addTrappedEventListener</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"> targetContainer</span><span class="token operator" style="color:#393A34">:</span><span class="token plain"> </span><span class="token maybe-class-name">EventTarget</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"> domEventName</span><span class="token operator" style="color:#393A34">:</span><span class="token plain"> </span><span class="token maybe-class-name">DOMEventName</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"> eventSystemFlags</span><span class="token operator" style="color:#393A34">:</span><span class="token plain"> </span><span class="token maybe-class-name">EventSystemFlags</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"> isCapturePhaseListener</span><span class="token operator" style="color:#393A34">:</span><span class="token plain"> </span><span class="token builtin">boolean</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><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" style="color:#00009f">let</span><span class="token plain"> listener </span><span class="token operator" style="color:#393A34">=</span><span class="token plain"> </span><span class="token function" style="color:#d73a49">createEventListenerWrapperWithPriority</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"> targetContainer</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"> domEventName</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"> eventSystemFlags</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 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 comment" style="color:#999988;font-style:italic">// ...</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 control-flow" style="color:#00009f">if</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">(</span><span class="token plain">isCapturePhaseListener</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 function" style="color:#d73a49">addEventCaptureListener</span><span class="token punctuation" style="color:#393A34">(</span><span class="token plain">targetContainer</span><span class="token punctuation" style="color:#393A34">,</span><span class="token plain"> domEventName</span><span class="token punctuation" style="color:#393A34">,</span><span class="token plain"> listener</span><span class="token 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><span class="token keyword control-flow" style="color:#00009f">else</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 function" style="color:#d73a49">addEventBubbleListener</span><span class="token punctuation" style="color:#393A34">(</span><span class="token plain">targetContainer</span><span class="token punctuation" style="color:#393A34">,</span><span class="token plain"> domEventName</span><span class="token punctuation" style="color:#393A34">,</span><span class="token plain"> listener</span><span class="token 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"></span><span class="token punctuation" style="color:#393A34">}</span><br></span></code></pre><button type="button" aria-label="Copy code to clipboard" title="Copy" class="copyButton_eDfN clean-btn"><span class="copyButtonIcons_W9eQ" aria-hidden="true"><svg class="copyButtonIcon_XEyF" 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_i9w9" 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><p>基于以上流程可知，调用 ReactDOM.createRoot 方法时，就已经在 root 节点上初始化所有原生事件的监听回调函数。而不是在组件上写合成事件的监听时，才开始注册事件回调。</p><h4 class="anchor anchorWithHideOnScrollNavbar_R0VQ" id="22-react-事件的触发">2.2 React 事件的触发<a class="hash-link" href="#22-react-事件的触发" title="Direct link to heading"></a></h4><p><img loading="lazy" src="https://user-images.githubusercontent.com/17002181/144073503-a8a2eb15-a2e7-4d98-9f0e-ef2a6b5c0738.png" class="img_E7b_"></p><p>在注册事件阶段调用的 addTrappedEventListener 方法中，会使用 createEventListenerWrapperWithPriority 函数来创建事件回调。createEventListenerWrapperWithPriority 函数根据事件类型，划分出若干个不同优先级的 dispathEvent。事件回调最终都调用进 dispatchEvent 方法。</p><p>因此触发一个原生事件时，大致的执行流程如下：</p><ol><li>原生事件触发后，进入 dispatchEvent 回调方法；</li><li>attemptToDispatchEvent 方法根据该原生事件查找到当前原生 Dom 节点和映射的 Fiber 节点；</li><li>事件和 Fiber 等信息被派发给插件系统进行处理，插件系统调用各插件暴露的 extractEvents 方法；</li><li>accumulateSinglePhaseListeners 方法向上收集 Fiber 树上监听相关事件的其他回调函数，构造合成事件并加入到派发队列 dispatchQueue 中；</li><li>调用 processDispatchQueue 方法，基于捕获或冒泡阶段的标识，按倒序或顺序执行 dispatchQueue 中的方法；</li></ol><h2 class="anchor anchorWithHideOnScrollNavbar_R0VQ" id="参考资料">参考资料<a class="hash-link" href="#参考资料" title="Direct link to heading"></a></h2><ol><li><a href="https://reactjs.org/docs/events.html" target="_blank" rel="noopener noreferrer">SyntheticEvent</a></li><li><a href="https://reactjs.org/docs/handling-events.html" target="_blank" rel="noopener noreferrer">Handling Events</a></li><li><a href="https://www.w3.org/TR/DOM-Level-3-Events" target="_blank" rel="noopener noreferrer">UI Events</a></li></ol></div></article><nav class="pagination-nav docusaurus-mt-lg" aria-label="Docs pages navigation"><div class="pagination-nav__item"><a class="pagination-nav__link" href="/awesome-interview/book4/engineer-mfa"><div class="pagination-nav__sublabel">Previous</div><div class="pagination-nav__label">工程化：谈谈微前端</div></a></div><div class="pagination-nav__item pagination-nav__item--next"><a class="pagination-nav__link" href="/awesome-interview/book4/frame-react-vs-vue"><div class="pagination-nav__sublabel">Next</div><div class="pagination-nav__label">框架：谈谈 React 和 Vue 的区别</div></a></div></nav></div></div><div class="col col--3"><div class="tableOfContents_cNA8 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-原生事件和合成事件" class="table-of-contents__link toc-highlight">1. 原生事件和合成事件</a><ul><li><a href="#11-原生事件" class="table-of-contents__link toc-highlight">1.1 原生事件</a></li><li><a href="#12-react-合成事件" class="table-of-contents__link toc-highlight">1.2 React 合成事件</a></li></ul></li><li><a href="#2-react-事件机制" class="table-of-contents__link toc-highlight">2. React 事件机制</a><ul><li><a href="#21-react-事件的注册" class="table-of-contents__link toc-highlight">2.1 React 事件的注册</a></li><li><a href="#22-react-事件的触发" class="table-of-contents__link toc-highlight">2.2 React 事件的触发</a></li></ul></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.16895322.js"></script>
|
||
<script src="/awesome-interview/assets/js/main.a6349f88.js"></script>
|
||
</body>
|
||
</html> |