study/ZiuChen.github.io
1
0
Fork 0
mirror of https://github.com/ZiuChen/ZiuChen.github.io.git synced 2025-08-24 12:13:56 +08:00
Code Issues Packages Projects Releases Wiki Activity
ZiuChen.github.io/note/React Hooks.html

303 lines
158 KiB
HTML
Raw Blame History

This file contains invisible Unicode characters

This file contains invisible Unicode characters that are indistinguishable to humans but may be processed differently by a computer. If you think that this is intentional, you can safely ignore this warning. Use the Escape button to reveal them.

This file contains Unicode characters that might be confused with other characters. If you think that this is intentional, you can safely ignore this warning. Use the Escape button to reveal them.

<!DOCTYPE html>
<html lang="en-US" dir="ltr">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width,initial-scale=1">
<title>React Hooks | ZiuChen</title>
<meta name="description" content="Unlimited Progress.">
<link rel="preload stylesheet" href="/assets/style.10d30366.css" as="style">
<script type="module" src="/assets/app.bdd8a2bd.js"></script>
<link rel="preload" href="/assets/inter-roman-latin.2ed14f66.woff2" as="font" type="font/woff2" crossorigin="">
<link rel="modulepreload" href="/assets/chunks/framework.a304f0f7.js">
<link rel="modulepreload" href="/assets/chunks/theme.f2bdac91.js">
<link rel="modulepreload" href="/assets/note_React Hooks.md.1ee13841.lean.js">
<link rel="icon" href="/logo.png">
<script id="check-dark-light">(()=>{const e=localStorage.getItem("vitepress-theme-appearance")||"",a=window.matchMedia("(prefers-color-scheme: dark)").matches;(!e||e==="auto"?a:e==="dark")&&document.documentElement.classList.add("dark")})();</script>
</head>
<body>
<div id="app"><div class="Layout" data-v-6305e88a><!--[--><!--]--><!--[--><span tabindex="-1" data-v-4dd3ce25></span><a href="#VPContent" class="VPSkipLink visually-hidden" data-v-4dd3ce25> Skip to content </a><!--]--><!----><header class="VPNav" data-v-6305e88a data-v-a35c4512><div class="VPNavBar has-sidebar" data-v-a35c4512 data-v-177342c2><div class="container" data-v-177342c2><div class="title" data-v-177342c2><div class="VPNavBarTitle has-sidebar" data-v-177342c2 data-v-aca9ebf6><a class="title" href="/" data-v-aca9ebf6><!--[--><!--]--><!--[--><img class="VPImage logo" src="/logo.png" alt data-v-5113f303><!--]--><!--[-->ZiuChen<!--]--><!--[--><!--]--></a></div></div><div class="content" data-v-177342c2><div class="curtain" data-v-177342c2></div><div class="content-body" data-v-177342c2><!--[--><!--]--><div class="VPNavBarSearch search" style="--vp-meta-key:&#39;Meta&#39;;" data-v-177342c2><!--[--><div id="docsearch"><button type="button" class="DocSearch DocSearch-Button" aria-label="Search"><span class="DocSearch-Button-Container"><svg class="DocSearch-Search-Icon" width="20" height="20" viewBox="0 0 20 20" aria-label="search icon"><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"><kbd class="DocSearch-Button-Key"></kbd><kbd class="DocSearch-Button-Key">K</kbd></span></button></div><!--]--></div><nav aria-labelledby="main-nav-aria-label" class="VPNavBarMenu menu" data-v-177342c2 data-v-0725df7f><span id="main-nav-aria-label" class="visually-hidden" data-v-0725df7f>Main Navigation</span><!--[--><!--[--><a class="VPLink link VPNavBarMenuLink" href="/" tabindex="0" data-v-0725df7f data-v-54fa8d63 data-v-fd6e3585><!--[-->首页<!--]--><!----></a><!--]--><!--[--><div class="VPFlyout VPNavBarMenuGroup" data-v-0725df7f data-v-93bf11df><button type="button" class="button" aria-haspopup="true" aria-expanded="false" data-v-93bf11df><span class="text" data-v-93bf11df><!----> 我的项目 <svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" viewbox="0 0 24 24" class="text-icon" data-v-93bf11df><path d="M12,16c-0.3,0-0.5-0.1-0.7-0.3l-6-6c-0.4-0.4-0.4-1,0-1.4s1-0.4,1.4,0l5.3,5.3l5.3-5.3c0.4-0.4,1-0.4,1.4,0s0.4,1,0,1.4l-6,6C12.5,15.9,12.3,16,12,16z"></path></svg></span></button><div class="menu" data-v-93bf11df><div class="VPMenu" data-v-93bf11df data-v-fb66cf11><div class="items" data-v-fb66cf11><!--[--><!--[--><div class="VPMenuLink" data-v-fb66cf11 data-v-504c1659><a class="VPLink link" href="/project/ClipboardManager/" data-v-504c1659 data-v-fd6e3585><!--[-->超级剪贴板<!--]--><!----></a></div><!--]--><!--[--><div class="VPMenuLink" data-v-fb66cf11 data-v-504c1659><a class="VPLink link" href="/project/Markdown/" data-v-504c1659 data-v-fd6e3585><!--[-->超级Markdown<!--]--><!----></a></div><!--]--><!--[--><div class="VPMenuLink" data-v-fb66cf11 data-v-504c1659><a class="VPLink link" href="/project/JSRunner/" data-v-504c1659 data-v-fd6e3585><!--[-->超级JavaScript<!--]--><!----></a></div><!--]--><!--[--><div class="VPMenuLink" data-v-fb66cf11 data-v-504c1659><a class="VPLink link" href="/project/SmartWordBreak/" data-v-504c1659 data-v-fd6e3585><!--[-->超级分词<!--]--><!----></a></div><!--]--><!--]--></div><!--[--><!--]--></div></div></div><!--]--><!--[--><div class="VPFlyout VPNavBarMenuGroup" data-v-0725df7f data-v-93bf11df><button type="button" class="button" aria-haspopup="true" aria-expanded="false" data-v-93bf11df><span class="text" data-v-93bf11df><!----> 开源作品 <svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" viewbox="0 0 24 24" class="text-icon" data-v-93bf11df><path d="M12,16c-0.3,0-0.5-0.1-0.7-0.3l-6-6c-0.4-0.4-0.4-1,0-1.4s1-0.4,1.4,0l5.3,5.3l5.3-5.3c0.4-0.4,1-0.4,1.4,0s0.4,1,0,1.4l-6,6C12.5,15.9,12.3,16,12,16z"></path></svg></span></button><div class="menu" data-v-93bf11df><div class="VPMenu" data-v-93bf11df data-v-fb66cf11><div class="items" data-v-fb66cf11><!--[--><!--[--><div class="VPMenuLink" data-v-fb66cf11 data-v-504c1659><a class="VPLink link" href="/works/opensource.html" data-v-504c1659 data-v-fd6e3585><!--[-->个人作品<!--]--><!----></a></div><!--]--><!--[--><div class="VPMenuLink" data-v-fb66cf11 data-v-504c1659><a class="VPLink link" href="/works/contribution.html" data-v-504c1659 data-v-fd6e3585><!--[-->社区贡献<!--]--><!----></a></div><!--]--><!--]--></div><!--[--><!--]--></div></div></div><!--]--><!--[--><div class="VPFlyout VPNavBarMenuGroup" data-v-0725df7f data-v-93bf11df><button type="button" class="button" aria-haspopup="true" aria-expanded="false" data-v-93bf11df><span class="text" data-v-93bf11df><!----> 学习笔记 <svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" viewbox="0 0 24 24" class="text-icon" data-v-93bf11df><path d="M12,16c-0.3,0-0.5-0.1-0.7-0.3l-6-6c-0.4-0.4-0.4-1,0-1.4s1-0.4,1.4,0l5.3,5.3l5.3-5.3c0.4-0.4,1-0.4,1.4,0s0.4,1,0,1.4l-6,6C12.5,15.9,12.3,16,12,16z"></path></svg></span></button><div class="menu" data-v-93bf11df><div class="VPMenu" data-v-93bf11df data-v-fb66cf11><div class="items" data-v-fb66cf11><!--[--><!--[--><div class="VPMenuLink" data-v-fb66cf11 data-v-504c1659><a class="VPLink link" href="/note/JavaScript.html" data-v-504c1659 data-v-fd6e3585><!--[-->JavaScript基础<!--]--><!----></a></div><!--]--><!--[--><div class="VPMenuLink" data-v-fb66cf11 data-v-504c1659><a class="VPLink link" href="/note/CSS.html" data-v-504c1659 data-v-fd6e3585><!--[-->CSS基础<!--]--><!----></a></div><!--]--><!--[--><div class="VPMenuLink" data-v-fb66cf11 data-v-504c1659><a class="VPLink link" href="/note/JavaScriptEnhanced.html" data-v-504c1659 data-v-fd6e3585><!--[-->JavaScript进阶<!--]--><!----></a></div><!--]--><!--[--><div class="VPMenuLink" data-v-fb66cf11 data-v-504c1659><a class="VPLink link" href="/note/Front-end%20Engineering.html" data-v-504c1659 data-v-fd6e3585><!--[-->前端工程化<!--]--><!----></a></div><!--]--><!--[--><div class="VPMenuLink" data-v-fb66cf11 data-v-504c1659><a class="VPLink link" href="/note/SSR.html" data-v-504c1659 data-v-fd6e3585><!--[-->服务端渲染<!--]--><!----></a></div><!--]--><!--[--><div class="VPMenuLink" data-v-fb66cf11 data-v-504c1659><a class="VPLink link" href="/note/React.html" data-v-504c1659 data-v-fd6e3585><!--[-->React基础<!--]--><!----></a></div><!--]--><!--[--><div class="VPMenuLink" data-v-fb66cf11 data-v-504c1659><a class="VPLink link active" href="/note/React%20Hooks.html" data-v-504c1659 data-v-fd6e3585><!--[-->React Hooks<!--]--><!----></a></div><!--]--><!--[--><div class="VPMenuLink" data-v-fb66cf11 data-v-504c1659><a class="VPLink link" href="/note/Redux.html" data-v-504c1659 data-v-fd6e3585><!--[-->Redux<!--]--><!----></a></div><!--]--><!--[--><div class="VPMenuLink" data-v-fb66cf11 data-v-504c1659><a class="VPLink link" href="/note/React%20Router.html" data-v-504c1659 data-v-fd6e3585><!--[-->React Router<!--]--><!----></a></div><!--]--><!--[--><div class="VPMenuLink" data-v-fb66cf11 data-v-504c1659><a class="VPLink link" href="/note/MySQL.html" data-v-504c1659 data-v-fd6e3585><!--[-->MySQL<!--]--><!----></a></div><!--]--><!--]--></div><!--[--><!--]--></div></div></div><!--]--><!--[--><a class="VPLink link VPNavBarMenuLink" href="/self/" tabindex="0" data-v-0725df7f data-v-54fa8d63 data-v-fd6e3585><!--[-->个人介绍<!--]--><!----></a><!--]--><!--]--></nav><!----><div class="VPNavBarAppearance appearance" data-v-177342c2 data-v-140d7008><label title="toggle dark mode" data-v-140d7008 data-v-69cfd7b7><button class="VPSwitch VPSwitchAppearance" type="button" role="switch" aria-checked="false" data-v-69cfd7b7 data-v-2a85d626><span class="check" data-v-2a85d626><span class="icon" data-v-2a85d626><!--[--><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" viewbox="0 0 24 24" class="sun" data-v-69cfd7b7><path d="M12,18c-3.3,0-6-2.7-6-6s2.7-6,6-6s6,2.7,6,6S15.3,18,12,18zM12,8c-2.2,0-4,1.8-4,4c0,2.2,1.8,4,4,4c2.2,0,4-1.8,4-4C16,9.8,14.2,8,12,8z"></path><path d="M12,4c-0.6,0-1-0.4-1-1V1c0-0.6,0.4-1,1-1s1,0.4,1,1v2C13,3.6,12.6,4,12,4z"></path><path d="M12,24c-0.6,0-1-0.4-1-1v-2c0-0.6,0.4-1,1-1s1,0.4,1,1v2C13,23.6,12.6,24,12,24z"></path><path d="M5.6,6.6c-0.3,0-0.5-0.1-0.7-0.3L3.5,4.9c-0.4-0.4-0.4-1,0-1.4s1-0.4,1.4,0l1.4,1.4c0.4,0.4,0.4,1,0,1.4C6.2,6.5,5.9,6.6,5.6,6.6z"></path><path d="M19.8,20.8c-0.3,0-0.5-0.1-0.7-0.3l-1.4-1.4c-0.4-0.4-0.4-1,0-1.4s1-0.4,1.4,0l1.4,1.4c0.4,0.4,0.4,1,0,1.4C20.3,20.7,20,20.8,19.8,20.8z"></path><path d="M3,13H1c-0.6,0-1-0.4-1-1s0.4-1,1-1h2c0.6,0,1,0.4,1,1S3.6,13,3,13z"></path><path d="M23,13h-2c-0.6,0-1-0.4-1-1s0.4-1,1-1h2c0.6,0,1,0.4,1,1S23.6,13,23,13z"></path><path d="M4.2,20.8c-0.3,0-0.5-0.1-0.7-0.3c-0.4-0.4-0.4-1,0-1.4l1.4-1.4c0.4-0.4,1-0.4,1.4,0s0.4,1,0,1.4l-1.4,1.4C4.7,20.7,4.5,20.8,4.2,20.8z"></path><path d="M18.4,6.6c-0.3,0-0.5-0.1-0.7-0.3c-0.4-0.4-0.4-1,0-1.4l1.4-1.4c0.4-0.4,1-0.4,1.4,0s0.4,1,0,1.4l-1.4,1.4C18.9,6.5,18.6,6.6,18.4,6.6z"></path></svg><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" viewbox="0 0 24 24" class="moon" data-v-69cfd7b7><path d="M12.1,22c-0.3,0-0.6,0-0.9,0c-5.5-0.5-9.5-5.4-9-10.9c0.4-4.8,4.2-8.6,9-9c0.4,0,0.8,0.2,1,0.5c0.2,0.3,0.2,0.8-0.1,1.1c-2,2.7-1.4,6.4,1.3,8.4c2.1,1.6,5,1.6,7.1,0c0.3-0.2,0.7-0.3,1.1-0.1c0.3,0.2,0.5,0.6,0.5,1c-0.2,2.7-1.5,5.1-3.6,6.8C16.6,21.2,14.4,22,12.1,22zM9.3,4.4c-2.9,1-5,3.6-5.2,6.8c-0.4,4.4,2.8,8.3,7.2,8.7c2.1,0.2,4.2-0.4,5.8-1.8c1.1-0.9,1.9-2.1,2.4-3.4c-2.5,0.9-5.3,0.5-7.5-1.1C9.2,11.4,8.1,7.7,9.3,4.4z"></path></svg><!--]--></span></span></button></label></div><div class="VPSocialLinks VPNavBarSocialLinks social-links" data-v-177342c2 data-v-598000f3 data-v-efa5999f><!--[--><a class="VPSocialLink" href="https://github.com/ZiuChen" aria-label="github" target="_blank" rel="noopener" data-v-efa5999f data-v-88a75067><svg role="img" viewBox="0 0 24 24" xmlns="http://www.w3.org/2000/svg"><title>GitHub</title><path d="M12 .297c-6.63 0-12 5.373-12 12 0 5.303 3.438 9.8 8.205 11.385.6.113.82-.258.82-.577 0-.285-.01-1.04-.015-2.04-3.338.724-4.042-1.61-4.042-1.61C4.422 18.07 3.633 17.7 3.633 17.7c-1.087-.744.084-.729.084-.729 1.205.084 1.838 1.236 1.838 1.236 1.07 1.835 2.809 1.305 3.495.998.108-.776.417-1.305.76-1.605-2.665-.3-5.466-1.332-5.466-5.93 0-1.31.465-2.38 1.235-3.22-.135-.303-.54-1.523.105-3.176 0 0 1.005-.322 3.3 1.23.96-.267 1.98-.399 3-.405 1.02.006 2.04.138 3 .405 2.28-1.552 3.285-1.23 3.285-1.23.645 1.653.24 2.873.12 3.176.765.84 1.23 1.91 1.23 3.22 0 4.61-2.805 5.625-5.475 5.92.42.36.81 1.096.81 2.22 0 1.606-.015 2.896-.015 3.286 0 .315.21.69.825.57C20.565 22.092 24 17.592 24 12.297c0-6.627-5.373-12-12-12"/></svg></a><a class="VPSocialLink" href="https://juejin.cn/user/1887205216238477" aria-label target="_blank" rel="noopener" data-v-efa5999f data-v-88a75067><svg width="36" height="28" viewBox="0 0 36 28" fill="none" xmlns="http://www.w3.org/2000/svg"><path fill-rule="evenodd" clip-rule="evenodd" d="M17.5875 6.77268L21.8232 3.40505L17.5875 0.00748237L17.5837 0L13.3555 3.39757L17.5837 6.76894L17.5875 6.77268ZM17.5863 17.3955H17.59L28.5161 8.77432L25.5526 6.39453L17.59 12.6808H17.5863L17.5825 12.6845L9.61993 6.40201L6.66016 8.78181L17.5825 17.3992L17.5863 17.3955ZM17.5828 23.2891L17.5865 23.2854L32.2133 11.7456L35.1768 14.1254L28.5238 19.3752L17.5865 28L0.284376 14.3574L0 14.1291L2.95977 11.7531L17.5828 23.2891Z" fill="#1E80FF"/></svg></a><!--]--></div><div class="VPFlyout VPNavBarExtra extra" data-v-177342c2 data-v-4ef5f3a8 data-v-93bf11df><button type="button" class="button" aria-haspopup="true" aria-expanded="false" aria-label="extra navigation" data-v-93bf11df><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" viewbox="0 0 24 24" class="icon" data-v-93bf11df><circle cx="12" cy="12" r="2"></circle><circle cx="19" cy="12" r="2"></circle><circle cx="5" cy="12" r="2"></circle></svg></button><div class="menu" data-v-93bf11df><div class="VPMenu" data-v-93bf11df data-v-fb66cf11><!----><!--[--><!--[--><!----><div class="group" data-v-4ef5f3a8><div class="item appearance" data-v-4ef5f3a8><p class="label" data-v-4ef5f3a8>Appearance</p><div class="appearance-action" data-v-4ef5f3a8><label title="toggle dark mode" data-v-4ef5f3a8 data-v-69cfd7b7><button class="VPSwitch VPSwitchAppearance" type="button" role="switch" aria-checked="false" data-v-69cfd7b7 data-v-2a85d626><span class="check" data-v-2a85d626><span class="icon" data-v-2a85d626><!--[--><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" viewbox="0 0 24 24" class="sun" data-v-69cfd7b7><path d="M12,18c-3.3,0-6-2.7-6-6s2.7-6,6-6s6,2.7,6,6S15.3,18,12,18zM12,8c-2.2,0-4,1.8-4,4c0,2.2,1.8,4,4,4c2.2,0,4-1.8,4-4C16,9.8,14.2,8,12,8z"></path><path d="M12,4c-0.6,0-1-0.4-1-1V1c0-0.6,0.4-1,1-1s1,0.4,1,1v2C13,3.6,12.6,4,12,4z"></path><path d="M12,24c-0.6,0-1-0.4-1-1v-2c0-0.6,0.4-1,1-1s1,0.4,1,1v2C13,23.6,12.6,24,12,24z"></path><path d="M5.6,6.6c-0.3,0-0.5-0.1-0.7-0.3L3.5,4.9c-0.4-0.4-0.4-1,0-1.4s1-0.4,1.4,0l1.4,1.4c0.4,0.4,0.4,1,0,1.4C6.2,6.5,5.9,6.6,5.6,6.6z"></path><path d="M19.8,20.8c-0.3,0-0.5-0.1-0.7-0.3l-1.4-1.4c-0.4-0.4-0.4-1,0-1.4s1-0.4,1.4,0l1.4,1.4c0.4,0.4,0.4,1,0,1.4C20.3,20.7,20,20.8,19.8,20.8z"></path><path d="M3,13H1c-0.6,0-1-0.4-1-1s0.4-1,1-1h2c0.6,0,1,0.4,1,1S3.6,13,3,13z"></path><path d="M23,13h-2c-0.6,0-1-0.4-1-1s0.4-1,1-1h2c0.6,0,1,0.4,1,1S23.6,13,23,13z"></path><path d="M4.2,20.8c-0.3,0-0.5-0.1-0.7-0.3c-0.4-0.4-0.4-1,0-1.4l1.4-1.4c0.4-0.4,1-0.4,1.4,0s0.4,1,0,1.4l-1.4,1.4C4.7,20.7,4.5,20.8,4.2,20.8z"></path><path d="M18.4,6.6c-0.3,0-0.5-0.1-0.7-0.3c-0.4-0.4-0.4-1,0-1.4l1.4-1.4c0.4-0.4,1-0.4,1.4,0s0.4,1,0,1.4l-1.4,1.4C18.9,6.5,18.6,6.6,18.4,6.6z"></path></svg><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" viewbox="0 0 24 24" class="moon" data-v-69cfd7b7><path d="M12.1,22c-0.3,0-0.6,0-0.9,0c-5.5-0.5-9.5-5.4-9-10.9c0.4-4.8,4.2-8.6,9-9c0.4,0,0.8,0.2,1,0.5c0.2,0.3,0.2,0.8-0.1,1.1c-2,2.7-1.4,6.4,1.3,8.4c2.1,1.6,5,1.6,7.1,0c0.3-0.2,0.7-0.3,1.1-0.1c0.3,0.2,0.5,0.6,0.5,1c-0.2,2.7-1.5,5.1-3.6,6.8C16.6,21.2,14.4,22,12.1,22zM9.3,4.4c-2.9,1-5,3.6-5.2,6.8c-0.4,4.4,2.8,8.3,7.2,8.7c2.1,0.2,4.2-0.4,5.8-1.8c1.1-0.9,1.9-2.1,2.4-3.4c-2.5,0.9-5.3,0.5-7.5-1.1C9.2,11.4,8.1,7.7,9.3,4.4z"></path></svg><!--]--></span></span></button></label></div></div></div><div class="group" data-v-4ef5f3a8><div class="item social-links" data-v-4ef5f3a8><div class="VPSocialLinks social-links-list" data-v-4ef5f3a8 data-v-efa5999f><!--[--><a class="VPSocialLink" href="https://github.com/ZiuChen" aria-label="github" target="_blank" rel="noopener" data-v-efa5999f data-v-88a75067><svg role="img" viewBox="0 0 24 24" xmlns="http://www.w3.org/2000/svg"><title>GitHub</title><path d="M12 .297c-6.63 0-12 5.373-12 12 0 5.303 3.438 9.8 8.205 11.385.6.113.82-.258.82-.577 0-.285-.01-1.04-.015-2.04-3.338.724-4.042-1.61-4.042-1.61C4.422 18.07 3.633 17.7 3.633 17.7c-1.087-.744.084-.729.084-.729 1.205.084 1.838 1.236 1.838 1.236 1.07 1.835 2.809 1.305 3.495.998.108-.776.417-1.305.76-1.605-2.665-.3-5.466-1.332-5.466-5.93 0-1.31.465-2.38 1.235-3.22-.135-.303-.54-1.523.105-3.176 0 0 1.005-.322 3.3 1.23.96-.267 1.98-.399 3-.405 1.02.006 2.04.138 3 .405 2.28-1.552 3.285-1.23 3.285-1.23.645 1.653.24 2.873.12 3.176.765.84 1.23 1.91 1.23 3.22 0 4.61-2.805 5.625-5.475 5.92.42.36.81 1.096.81 2.22 0 1.606-.015 2.896-.015 3.286 0 .315.21.69.825.57C20.565 22.092 24 17.592 24 12.297c0-6.627-5.373-12-12-12"/></svg></a><a class="VPSocialLink" href="https://juejin.cn/user/1887205216238477" aria-label target="_blank" rel="noopener" data-v-efa5999f data-v-88a75067><svg width="36" height="28" viewBox="0 0 36 28" fill="none" xmlns="http://www.w3.org/2000/svg"><path fill-rule="evenodd" clip-rule="evenodd" d="M17.5875 6.77268L21.8232 3.40505L17.5875 0.00748237L17.5837 0L13.3555 3.39757L17.5837 6.76894L17.5875 6.77268ZM17.5863 17.3955H17.59L28.5161 8.77432L25.5526 6.39453L17.59 12.6808H17.5863L17.5825 12.6845L9.61993 6.40201L6.66016 8.78181L17.5825 17.3992L17.5863 17.3955ZM17.5828 23.2891L17.5865 23.2854L32.2133 11.7456L35.1768 14.1254L28.5238 19.3752L17.5865 28L0.284376 14.3574L0 14.1291L2.95977 11.7531L17.5828 23.2891Z" fill="#1E80FF"/></svg></a><!--]--></div></div></div><!--]--><!--]--></div></div></div><!--[--><!--]--><button type="button" class="VPNavBarHamburger hamburger" aria-label="mobile navigation" aria-expanded="false" aria-controls="VPNavScreen" data-v-177342c2 data-v-432ccc50><span class="container" data-v-432ccc50><span class="top" data-v-432ccc50></span><span class="middle" data-v-432ccc50></span><span class="bottom" data-v-432ccc50></span></span></button></div></div></div></div><!----></header><div class="VPLocalNav" data-v-6305e88a data-v-756dcc9b><button class="menu" aria-expanded="false" aria-controls="VPSidebarNav" data-v-756dcc9b><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" viewbox="0 0 24 24" class="menu-icon" data-v-756dcc9b><path d="M17,11H3c-0.6,0-1-0.4-1-1s0.4-1,1-1h14c0.6,0,1,0.4,1,1S17.6,11,17,11z"></path><path d="M21,7H3C2.4,7,2,6.6,2,6s0.4-1,1-1h18c0.6,0,1,0.4,1,1S21.6,7,21,7z"></path><path d="M21,15H3c-0.6,0-1-0.4-1-1s0.4-1,1-1h18c0.6,0,1,0.4,1,1S21.6,15,21,15z"></path><path d="M17,19H3c-0.6,0-1-0.4-1-1s0.4-1,1-1h14c0.6,0,1,0.4,1,1S17.6,19,17,19z"></path></svg><span class="menu-text" data-v-756dcc9b>Menu</span></button><div class="VPLocalNavOutlineDropdown" style="--vp-vh:0px;" data-v-756dcc9b data-v-c8c65e5a><button data-v-c8c65e5a>Return to top</button><!----></div></div><aside class="VPSidebar" data-v-6305e88a data-v-5081c0c7><div class="curtain" data-v-5081c0c7></div><nav class="nav" id="VPSidebarNav" aria-labelledby="sidebar-aria-label" tabindex="-1" data-v-5081c0c7><span class="visually-hidden" id="sidebar-aria-label" data-v-5081c0c7> Sidebar Navigation </span><!--[--><!--]--><!--[--><div class="group" data-v-5081c0c7><section class="VPSidebarItem level-0" data-v-5081c0c7 data-v-79816cba><div class="item" role="button" tabindex="0" data-v-79816cba><div class="indicator" data-v-79816cba></div><h2 class="text" data-v-79816cba>我的项目</h2><!----></div><div class="items" data-v-79816cba><!--[--><div class="VPSidebarItem level-1 is-link" data-v-79816cba data-v-79816cba><div class="item" data-v-79816cba><div class="indicator" data-v-79816cba></div><a class="VPLink link link" href="/project/ClipboardManager/" data-v-79816cba data-v-fd6e3585><!--[--><p class="text" data-v-79816cba>超级剪贴板</p><!--]--><!----></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-79816cba data-v-79816cba><div class="item" data-v-79816cba><div class="indicator" data-v-79816cba></div><a class="VPLink link link" href="/project/Markdown/" data-v-79816cba data-v-fd6e3585><!--[--><p class="text" data-v-79816cba>超级Markdown</p><!--]--><!----></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-79816cba data-v-79816cba><div class="item" data-v-79816cba><div class="indicator" data-v-79816cba></div><a class="VPLink link link" href="/project/JSRunner/" data-v-79816cba data-v-fd6e3585><!--[--><p class="text" data-v-79816cba>超级JavaScript</p><!--]--><!----></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-79816cba data-v-79816cba><div class="item" data-v-79816cba><div class="indicator" data-v-79816cba></div><a class="VPLink link link" href="/project/SmartWordBreak/" data-v-79816cba data-v-fd6e3585><!--[--><p class="text" data-v-79816cba>超级分词</p><!--]--><!----></a><!----></div><!----></div><!--]--></div></section></div><div class="group" data-v-5081c0c7><section class="VPSidebarItem level-0 collapsible collapsed" data-v-5081c0c7 data-v-79816cba><div class="item" role="button" tabindex="0" data-v-79816cba><div class="indicator" data-v-79816cba></div><h2 class="text" data-v-79816cba>开源作品</h2><div class="caret" role="button" aria-label="toggle section" tabindex="0" data-v-79816cba><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" viewbox="0 0 24 24" class="caret-icon" data-v-79816cba><path d="M9,19c-0.3,0-0.5-0.1-0.7-0.3c-0.4-0.4-0.4-1,0-1.4l5.3-5.3L8.3,6.7c-0.4-0.4-0.4-1,0-1.4s1-0.4,1.4,0l6,6c0.4,0.4,0.4,1,0,1.4l-6,6C9.5,18.9,9.3,19,9,19z"></path></svg></div></div><div class="items" data-v-79816cba><!--[--><div class="VPSidebarItem level-1 is-link" data-v-79816cba data-v-79816cba><div class="item" data-v-79816cba><div class="indicator" data-v-79816cba></div><a class="VPLink link link" href="/works/opensource.html" data-v-79816cba data-v-fd6e3585><!--[--><p class="text" data-v-79816cba>个人作品</p><!--]--><!----></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-79816cba data-v-79816cba><div class="item" data-v-79816cba><div class="indicator" data-v-79816cba></div><a class="VPLink link link" href="/works/contribution.html" data-v-79816cba data-v-fd6e3585><!--[--><p class="text" data-v-79816cba>社区贡献</p><!--]--><!----></a><!----></div><!----></div><!--]--></div></section></div><div class="group" data-v-5081c0c7><section class="VPSidebarItem level-0 collapsible collapsed" data-v-5081c0c7 data-v-79816cba><div class="item" role="button" tabindex="0" data-v-79816cba><div class="indicator" data-v-79816cba></div><h2 class="text" data-v-79816cba>文章归档</h2><div class="caret" role="button" aria-label="toggle section" tabindex="0" data-v-79816cba><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" viewbox="0 0 24 24" class="caret-icon" data-v-79816cba><path d="M9,19c-0.3,0-0.5-0.1-0.7-0.3c-0.4-0.4-0.4-1,0-1.4l5.3-5.3L8.3,6.7c-0.4-0.4-0.4-1,0-1.4s1-0.4,1.4,0l6,6c0.4,0.4,0.4,1,0,1.4l-6,6C9.5,18.9,9.3,19,9,19z"></path></svg></div></div><div class="items" data-v-79816cba><!--[--><div class="VPSidebarItem level-1 is-link" data-v-79816cba data-v-79816cba><div class="item" data-v-79816cba><div class="indicator" data-v-79816cba></div><a class="VPLink link link" href="/article/%E3%80%902023%E3%80%91%E9%9D%92%E8%AE%AD%E8%90%A5%20-%20%E5%89%8D%E7%AB%AF%E7%BB%83%E4%B9%A0%E9%A2%98%E6%B1%87%E6%80%BB%E8%A7%A3%E6%9E%90.html" data-v-79816cba data-v-fd6e3585><!--[--><p class="text" data-v-79816cba>【2023】青训营 - 前端练习题汇总解析</p><!--]--><!----></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-79816cba data-v-79816cba><div class="item" data-v-79816cba><div class="indicator" data-v-79816cba></div><a class="VPLink link link" href="/article/%E3%80%90%E5%AD%97%E8%8A%82%E8%B7%B3%E5%8A%A8%E3%80%91%E5%89%8D%E7%AB%AF%E9%9D%A2%E8%AF%95%E9%A2%98%E6%80%BB%E7%BB%93.html" data-v-79816cba data-v-fd6e3585><!--[--><p class="text" data-v-79816cba>【字节跳动】前端面试题总结</p><!--]--><!----></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-79816cba data-v-79816cba><div class="item" data-v-79816cba><div class="indicator" data-v-79816cba></div><a class="VPLink link link" href="/article/%E3%80%90%E5%BF%AB%E6%89%8B%E3%80%91%E6%B7%B1%E5%85%A5%E7%90%86%E8%A7%A3%E5%89%8D%E7%AB%AF%E9%9D%A2%E8%AF%95%E9%A2%98.html" data-v-79816cba data-v-fd6e3585><!--[--><p class="text" data-v-79816cba>【快手】深入理解前端面试题</p><!--]--><!----></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-79816cba data-v-79816cba><div class="item" data-v-79816cba><div class="indicator" data-v-79816cba></div><a class="VPLink link link" href="/article/%E3%80%90%E7%94%A8%E5%8F%8B%E9%87%91%E8%9E%8D%E3%80%91%E5%89%8D%E7%AB%AF%E9%9D%A2%E8%AF%95%E9%A2%98%E6%80%BB%E7%BB%93.html" data-v-79816cba data-v-fd6e3585><!--[--><p class="text" data-v-79816cba>【用友金融】前端面试题总结</p><!--]--><!----></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-79816cba data-v-79816cba><div class="item" data-v-79816cba><div class="indicator" data-v-79816cba></div><a class="VPLink link link" href="/article/%E4%B8%80%E6%96%87%E8%AF%BB%E6%87%82%E4%BA%8B%E4%BB%B6%E5%86%92%E6%B3%A1%E4%B8%8E%E4%BA%8B%E4%BB%B6%E6%8D%95%E8%8E%B7.html" data-v-79816cba data-v-fd6e3585><!--[--><p class="text" data-v-79816cba>一文读懂事件冒泡与事件捕获</p><!--]--><!----></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-79816cba data-v-79816cba><div class="item" data-v-79816cba><div class="indicator" data-v-79816cba></div><a class="VPLink link link" href="/article/%E4%B8%80%E6%96%87%E8%AF%BB%E6%87%82%E4%BC%AA%E7%B1%BB%E4%B8%8E%E4%BC%AA%E5%85%83%E7%B4%A0.html" data-v-79816cba data-v-fd6e3585><!--[--><p class="text" data-v-79816cba>一文读懂伪类与伪元素</p><!--]--><!----></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-79816cba data-v-79816cba><div class="item" data-v-79816cba><div class="indicator" data-v-79816cba></div><a class="VPLink link link" href="/article/%E4%B8%80%E6%96%87%E8%AF%BB%E6%87%82%E5%87%BD%E6%95%B0%E4%B8%ADthis%E6%8C%87%E5%90%91%E9%97%AE%E9%A2%98.html" data-v-79816cba data-v-fd6e3585><!--[--><p class="text" data-v-79816cba>一文读懂函数中this指向问题</p><!--]--><!----></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-79816cba data-v-79816cba><div class="item" data-v-79816cba><div class="indicator" data-v-79816cba></div><a class="VPLink link link" href="/article/%E4%BB%8E0%E5%AE%9E%E7%8E%B0%E4%B8%80%E4%B8%AA%E5%B9%B4%E5%BA%A6%E6%8A%A5%E5%91%8A.html" data-v-79816cba data-v-fd6e3585><!--[--><p class="text" data-v-79816cba>从0实现一个年度报告</p><!--]--><!----></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-79816cba data-v-79816cba><div class="item" data-v-79816cba><div class="indicator" data-v-79816cba></div><a class="VPLink link link" href="/article/%E5%BD%BB%E5%BA%95%E6%90%9E%E6%87%82%E5%AF%B9%E8%B1%A1%E7%9A%84%E6%95%B0%E6%8D%AE%E5%B1%9E%E6%80%A7%E6%8F%8F%E8%BF%B0%E7%AC%A6%E3%80%81%E5%AD%98%E5%82%A8%E5%B1%9E%E6%80%A7%E6%8F%8F%E8%BF%B0%E7%AC%A6.html" data-v-79816cba data-v-fd6e3585><!--[--><p class="text" data-v-79816cba>彻底搞懂对象的数据属性描述符、存储属性描述符</p><!--]--><!----></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-79816cba data-v-79816cba><div class="item" data-v-79816cba><div class="indicator" data-v-79816cba></div><a class="VPLink link link" href="/article/%E6%B5%85%E6%9E%90defineProperty%E4%B8%8EProxy%E5%AE%9E%E7%8E%B0%E7%9A%84%E5%8F%8C%E5%90%91%E7%BB%91%E5%AE%9A.html" data-v-79816cba data-v-fd6e3585><!--[--><p class="text" data-v-79816cba>浅析defineProperty与Proxy实现的双向绑定</p><!--]--><!----></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-79816cba data-v-79816cba><div class="item" data-v-79816cba><div class="indicator" data-v-79816cba></div><a class="VPLink link link" href="/article/%E6%B7%B1%E5%85%A5JavaScript%E6%95%B0%E6%8D%AE%E7%B1%BB%E5%9E%8B.html" data-v-79816cba data-v-fd6e3585><!--[--><p class="text" data-v-79816cba>深入JavaScript数据类型</p><!--]--><!----></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-79816cba data-v-79816cba><div class="item" data-v-79816cba><div class="indicator" data-v-79816cba></div><a class="VPLink link link" href="/article/%E6%B7%B1%E5%85%A5Vue3%E6%BA%90%E7%A0%81%EF%BC%8C%E7%9C%8B%E7%9C%8BVue.use%E5%90%8E%E7%A9%B6%E7%AB%9F%E5%8F%91%E7%94%9F%E4%BA%86%E4%BB%80%E4%B9%88%EF%BC%9F.html" data-v-79816cba data-v-fd6e3585><!--[--><p class="text" data-v-79816cba>深入Vue3源码，看看Vue.use后究竟发生了什么？</p><!--]--><!----></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-79816cba data-v-79816cba><div class="item" data-v-79816cba><div class="indicator" data-v-79816cba></div><a class="VPLink link link" href="/article/%E6%B7%B1%E5%85%A5%E7%90%86%E8%A7%A3Proxy%E4%B8%8EReflect.html" data-v-79816cba data-v-fd6e3585><!--[--><p class="text" data-v-79816cba>深入理解Proxy与Reflect</p><!--]--><!----></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-79816cba data-v-79816cba><div class="item" data-v-79816cba><div class="indicator" data-v-79816cba></div><a class="VPLink link link" href="/article/%E6%B7%B1%E5%85%A5%E7%90%86%E8%A7%A3%E6%B5%8F%E8%A7%88%E5%99%A8%E7%BC%93%E5%AD%98%E6%9C%BA%E5%88%B6.html" data-v-79816cba data-v-fd6e3585><!--[--><p class="text" data-v-79816cba>深入理解浏览器缓存机制</p><!--]--><!----></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-79816cba data-v-79816cba><div class="item" data-v-79816cba><div class="indicator" data-v-79816cba></div><a class="VPLink link link" href="/article/%E6%B7%B1%E5%85%A5%E7%90%86%E8%A7%A3%E6%B5%8F%E8%A7%88%E5%99%A8%E8%BF%90%E8%A1%8C%E5%8E%9F%E7%90%86.html" data-v-79816cba data-v-fd6e3585><!--[--><p class="text" data-v-79816cba>深入理解浏览器运行原理</p><!--]--><!----></a><!----></div><!----></div><!--]--></div></section></div><div class="group" data-v-5081c0c7><section class="VPSidebarItem level-0 collapsible has-active" data-v-5081c0c7 data-v-79816cba><div class="item" role="button" tabindex="0" data-v-79816cba><div class="indicator" data-v-79816cba></div><h2 class="text" data-v-79816cba>学习笔记</h2><div class="caret" role="button" aria-label="toggle section" tabindex="0" data-v-79816cba><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" viewbox="0 0 24 24" class="caret-icon" data-v-79816cba><path d="M9,19c-0.3,0-0.5-0.1-0.7-0.3c-0.4-0.4-0.4-1,0-1.4l5.3-5.3L8.3,6.7c-0.4-0.4-0.4-1,0-1.4s1-0.4,1.4,0l6,6c0.4,0.4,0.4,1,0,1.4l-6,6C9.5,18.9,9.3,19,9,19z"></path></svg></div></div><div class="items" data-v-79816cba><!--[--><div class="VPSidebarItem level-1 is-link" data-v-79816cba data-v-79816cba><div class="item" data-v-79816cba><div class="indicator" data-v-79816cba></div><a class="VPLink link link" href="/note/JavaScript.html" data-v-79816cba data-v-fd6e3585><!--[--><p class="text" data-v-79816cba>JavaScript基础</p><!--]--><!----></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-79816cba data-v-79816cba><div class="item" data-v-79816cba><div class="indicator" data-v-79816cba></div><a class="VPLink link link" href="/note/CSS.html" data-v-79816cba data-v-fd6e3585><!--[--><p class="text" data-v-79816cba>CSS基础</p><!--]--><!----></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-79816cba data-v-79816cba><div class="item" data-v-79816cba><div class="indicator" data-v-79816cba></div><a class="VPLink link link" href="/note/JavaScriptEnhanced.html" data-v-79816cba data-v-fd6e3585><!--[--><p class="text" data-v-79816cba>JavaScript进阶</p><!--]--><!----></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-79816cba data-v-79816cba><div class="item" data-v-79816cba><div class="indicator" data-v-79816cba></div><a class="VPLink link link" href="/note/Front-end%20Engineering.html" data-v-79816cba data-v-fd6e3585><!--[--><p class="text" data-v-79816cba>前端工程化</p><!--]--><!----></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-79816cba data-v-79816cba><div class="item" data-v-79816cba><div class="indicator" data-v-79816cba></div><a class="VPLink link link" href="/note/SSR.html" data-v-79816cba data-v-fd6e3585><!--[--><p class="text" data-v-79816cba>服务端渲染</p><!--]--><!----></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-79816cba data-v-79816cba><div class="item" data-v-79816cba><div class="indicator" data-v-79816cba></div><a class="VPLink link link" href="/note/React.html" data-v-79816cba data-v-fd6e3585><!--[--><p class="text" data-v-79816cba>React基础</p><!--]--><!----></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link is-active has-active" data-v-79816cba data-v-79816cba><div class="item" data-v-79816cba><div class="indicator" data-v-79816cba></div><a class="VPLink link link" href="/note/React%20Hooks.html" data-v-79816cba data-v-fd6e3585><!--[--><p class="text" data-v-79816cba>React Hooks</p><!--]--><!----></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-79816cba data-v-79816cba><div class="item" data-v-79816cba><div class="indicator" data-v-79816cba></div><a class="VPLink link link" href="/note/Redux.html" data-v-79816cba data-v-fd6e3585><!--[--><p class="text" data-v-79816cba>Redux</p><!--]--><!----></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-79816cba data-v-79816cba><div class="item" data-v-79816cba><div class="indicator" data-v-79816cba></div><a class="VPLink link link" href="/note/React%20Router.html" data-v-79816cba data-v-fd6e3585><!--[--><p class="text" data-v-79816cba>React Router</p><!--]--><!----></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-79816cba data-v-79816cba><div class="item" data-v-79816cba><div class="indicator" data-v-79816cba></div><a class="VPLink link link" href="/note/MySQL.html" data-v-79816cba data-v-fd6e3585><!--[--><p class="text" data-v-79816cba>MySQL</p><!--]--><!----></a><!----></div><!----></div><!--]--></div></section></div><!--]--><!--[--><!--]--></nav></aside><div class="VPContent has-sidebar" id="VPContent" data-v-6305e88a data-v-435404df><div class="VPDoc has-sidebar has-aside" data-v-435404df data-v-25140dfd><!--[--><!--]--><div class="container" data-v-25140dfd><div class="aside" data-v-25140dfd><div class="aside-curtain" data-v-25140dfd></div><div class="aside-container" data-v-25140dfd><div class="aside-content" data-v-25140dfd><div class="VPDocAside" data-v-25140dfd data-v-2b53d15f><!--[--><!--]--><!--[--><!--]--><div class="VPDocAsideOutline" data-v-2b53d15f data-v-1cf492a7><div class="content" data-v-1cf492a7><div class="outline-marker" data-v-1cf492a7></div><div class="outline-title" data-v-1cf492a7>On this page</div><nav aria-labelledby="doc-outline-aria-label" data-v-1cf492a7><span class="visually-hidden" id="doc-outline-aria-label" data-v-1cf492a7> Table of Contents for current page </span><ul class="root" data-v-1cf492a7 data-v-e09875d9><!--[--><!--]--></ul></nav></div></div><!--[--><!--]--><div class="spacer" data-v-2b53d15f></div><!--[--><!--]--><!----><!--[--><!--]--><!--[--><!--]--></div></div></div></div><div class="content" data-v-25140dfd><div class="content-container" data-v-25140dfd><!--[--><!--]--><!----><main class="main" data-v-25140dfd><div style="position:relative;" class="vp-doc _note_React%20Hooks" data-v-25140dfd><div><h1 id="react-hooks" tabindex="-1">React Hooks <a class="header-anchor" href="#react-hooks" aria-label="Permalink to &quot;React Hooks&quot;">​</a></h1><ul><li>认识和体验Hooks</li><li>State/Effect</li><li>Context/Reducer</li><li>Callback/Memo</li><li>Ref/LayoutEffect</li><li>自定义Hooks使用</li></ul><h2 id="认识react-hooks" tabindex="-1">认识React Hooks <a class="header-anchor" href="#认识react-hooks" aria-label="Permalink to &quot;认识React Hooks&quot;">​</a></h2><p>Hooks 是 React16.8 推出的新特性</p><p>在没有Hooks时，类组件能够完成的大部分工作，函数式组件都无法胜任：</p><ul><li>类组件可以定义并保存组件内部状态，并在状态发生改变时触发视图重新渲染 <ul><li>函数式组件不行，每次调用函数其中的变量都会被重新初始化，重新渲染时整个函数都重新执行</li></ul></li><li>类组件可以在其内部的生命周期回调中添加副作用 <ul><li>例如<code>componentDidMount</code>在类组件生命周期只会执行一次</li><li>函数式组件没有生命周期，如果在函数体内发起网络请求，那每次重新渲染都会发起请求</li></ul></li></ul><p>类组件存在的问题：</p><ul><li>复杂组件变得难以理解 <ul><li>业务代码相互耦合，类组件变得复杂</li><li>逻辑强耦合在一起难以拆分，强行拆分会导致过度设计，进一步增加代码复杂度</li></ul></li><li>class关键字的理解 <ul><li>初学React时class关键字理解存在困难</li><li>处理<code>this</code>的指向问题需要花费额外的心智负担</li></ul></li><li>组件状态复用 <ul><li>要复用组件需要借助高阶组件</li><li><code>redux</code> 中的 <code>connect</code> 或者 <code>react-router</code> 中的 <code>withRouter</code>，高阶组件的目的就是为了状态复</li><li>或通过Provider、Consumer来共享状态，但是Comsumer嵌套问题较严重</li></ul></li></ul><p>Hooks带来的优势：</p><ul><li>在不编写class的情况下使用state和其他React特性（如生命周期）</li><li>Hooks 允许我们在函数式组件中使用状态，并在状态发生改变时让视图重新渲染</li><li>同时，我们还可以在函数式组件中使用生命周期回调</li><li>更多的优点 ...</li></ul><h2 id="计数器案例对比" tabindex="-1">计数器案例对比 <a class="header-anchor" href="#计数器案例对比" aria-label="Permalink to &quot;计数器案例对比&quot;">​</a></h2><p>分别使用Hooks和类组件编写一个计数器：</p><div class="vp-code-group"><div class="tabs"><input type="radio" name="group-38eo7" id="tab-ZlAC9Jn" checked="checked"><label for="tab-ZlAC9Jn">CounterClass.jsx</label><input type="radio" name="group-38eo7" id="tab-f8lgMwi"><label for="tab-f8lgMwi">CounterFunctional.jsx</label></div><div class="blocks"><div class="language-tsx active line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">tsx</span><pre class="shiki material-theme-palenight"><code><span class="line"><span style="color:#676E95;font-style:italic;">// CounterClass.jsx</span></span>
<span class="line"><span style="color:#89DDFF;font-style:italic;">import</span><span style="color:#A6ACCD;"> React</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">PureComponent</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">}</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;font-style:italic;">from</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">react</span><span style="color:#89DDFF;">&#39;</span></span>
<span class="line"></span>
<span class="line"><span style="color:#89DDFF;font-style:italic;">export</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;font-style:italic;">default</span><span style="color:#A6ACCD;"> </span><span style="color:#C792EA;">class</span><span style="color:#A6ACCD;"> </span><span style="color:#FFCB6B;">CounterClass</span><span style="color:#A6ACCD;"> </span><span style="color:#C792EA;">extends</span><span style="color:#A6ACCD;"> </span><span style="color:#FFCB6B;">PureComponent</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#C792EA;">constructor</span><span style="color:#89DDFF;">()</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">super</span><span style="color:#F07178;">()</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">this.</span><span style="color:#A6ACCD;">state</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">=</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> count</span><span style="color:#89DDFF;">:</span><span style="color:#F07178;"> </span><span style="color:#F78C6C;">0</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">}</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">}</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#F07178;">setCount</span><span style="color:#89DDFF;">(</span><span style="color:#A6ACCD;font-style:italic;">num</span><span style="color:#89DDFF;">)</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">this.</span><span style="color:#82AAFF;">setState</span><span style="color:#F07178;">(</span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> count</span><span style="color:#89DDFF;">:</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">num</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">}</span><span style="color:#F07178;">)</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">}</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#F07178;">render</span><span style="color:#89DDFF;">()</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#C792EA;">const</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">{</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">count</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">}</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">=</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">this.</span><span style="color:#A6ACCD;">state</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;font-style:italic;">return</span><span style="color:#F07178;"> (</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">&lt;</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&lt;</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span><span style="color:#A6ACCD;">CounterClass</span><span style="color:#89DDFF;">&lt;/</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&lt;</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;{</span><span style="color:#A6ACCD;">count</span><span style="color:#89DDFF;">}&lt;/</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&lt;</span><span style="color:#F07178;">button</span><span style="color:#89DDFF;"> </span><span style="color:#C792EA;">onClick</span><span style="color:#89DDFF;">={()</span><span style="color:#A6ACCD;"> </span><span style="color:#C792EA;">=&gt;</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">this.</span><span style="color:#82AAFF;">setCount</span><span style="color:#A6ACCD;">(count </span><span style="color:#89DDFF;">+</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">1</span><span style="color:#A6ACCD;">)</span><span style="color:#89DDFF;">}&gt;</span><span style="color:#A6ACCD;">+1</span><span style="color:#89DDFF;">&lt;/</span><span style="color:#F07178;">button</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&lt;</span><span style="color:#F07178;">button</span><span style="color:#89DDFF;"> </span><span style="color:#C792EA;">onClick</span><span style="color:#89DDFF;">={()</span><span style="color:#A6ACCD;"> </span><span style="color:#C792EA;">=&gt;</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">this.</span><span style="color:#82AAFF;">setCount</span><span style="color:#A6ACCD;">(count </span><span style="color:#89DDFF;">-</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">1</span><span style="color:#A6ACCD;">)</span><span style="color:#89DDFF;">}&gt;</span><span style="color:#A6ACCD;">-1</span><span style="color:#89DDFF;">&lt;/</span><span style="color:#F07178;">button</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&lt;/</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#F07178;"> )</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">}</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br><span class="line-number">17</span><br><span class="line-number">18</span><br><span class="line-number">19</span><br><span class="line-number">20</span><br><span class="line-number">21</span><br><span class="line-number">22</span><br><span class="line-number">23</span><br><span class="line-number">24</span><br><span class="line-number">25</span><br><span class="line-number">26</span><br><span class="line-number">27</span><br></div></div><div class="language-tsx line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">tsx</span><pre class="shiki material-theme-palenight"><code><span class="line"><span style="color:#676E95;font-style:italic;">// CounterFunctional.jsx</span></span>
<span class="line"><span style="color:#89DDFF;font-style:italic;">import</span><span style="color:#A6ACCD;"> React</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">useState</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">}</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;font-style:italic;">from</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">react</span><span style="color:#89DDFF;">&#39;</span></span>
<span class="line"></span>
<span class="line"><span style="color:#89DDFF;font-style:italic;">export</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;font-style:italic;">default</span><span style="color:#A6ACCD;"> </span><span style="color:#C792EA;">function</span><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">CounterFunctional</span><span style="color:#89DDFF;">()</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#C792EA;">const</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">[</span><span style="color:#A6ACCD;">count</span><span style="color:#89DDFF;">,</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">setCount</span><span style="color:#89DDFF;">]</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">=</span><span style="color:#F07178;"> </span><span style="color:#82AAFF;">useState</span><span style="color:#F07178;">(</span><span style="color:#F78C6C;">0</span><span style="color:#F07178;">)</span></span>
<span class="line"></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;font-style:italic;">return</span><span style="color:#F07178;"> (</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">&lt;</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&lt;</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span><span style="color:#A6ACCD;">CounterFunctional</span><span style="color:#89DDFF;">&lt;/</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&lt;</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;{</span><span style="color:#A6ACCD;">count</span><span style="color:#89DDFF;">}&lt;/</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&lt;</span><span style="color:#F07178;">button</span><span style="color:#89DDFF;"> </span><span style="color:#C792EA;">onClick</span><span style="color:#89DDFF;">={()</span><span style="color:#A6ACCD;"> </span><span style="color:#C792EA;">=&gt;</span><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">setCount</span><span style="color:#A6ACCD;">(count </span><span style="color:#89DDFF;">+</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">1</span><span style="color:#A6ACCD;">)</span><span style="color:#89DDFF;">}&gt;</span><span style="color:#A6ACCD;">+1</span><span style="color:#89DDFF;">&lt;/</span><span style="color:#F07178;">button</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&lt;</span><span style="color:#F07178;">button</span><span style="color:#89DDFF;"> </span><span style="color:#C792EA;">onClick</span><span style="color:#89DDFF;">={()</span><span style="color:#A6ACCD;"> </span><span style="color:#C792EA;">=&gt;</span><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">setCount</span><span style="color:#A6ACCD;">(count </span><span style="color:#89DDFF;">-</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">1</span><span style="color:#A6ACCD;">)</span><span style="color:#89DDFF;">}&gt;</span><span style="color:#A6ACCD;">-1</span><span style="color:#89DDFF;">&lt;/</span><span style="color:#F07178;">button</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&lt;/</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#F07178;"> )</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br></div></div></div></div><h3 id="解读usestate" tabindex="-1">解读useState <a class="header-anchor" href="#解读usestate" aria-label="Permalink to &quot;解读useState&quot;">​</a></h3><p>Hook本质上就是一个JavaScript函数，这个函数可以帮你钩入（Hook Into） React State以及其他的生命周期回调</p><ul><li><p>只允许在函数顶层调用Hook，而不能再循环、条件判断或子函数中调用</p></li><li><p>只能在React的函数组件中调用Hook，不能在其他JavaScript函数中调用</p></li><li><p>从<code>react</code>导入<code>useState</code></p><ul><li>参数 状态初始值 不设置则为<code>undefined</code></li><li>返回值是一个数组 <ul><li>0位元素 <strong>当前状态的值</strong>，当函数第一次调用时为初始值</li><li>1位元素 设置状态值的函数</li></ul></li><li>当点击button按钮后，会完成两件事情： <ul><li>调用<code>setCount</code>函数，将状态设置为新的值</li><li>触发组件重新渲染（函数重新执行），使用新的state值渲染DOM</li></ul></li></ul></li><li><p>为什么叫<code>useState</code>而不叫<code>createState</code>？</p><ul><li>create的含义不是很明确，因为state仅在组件首次渲染时被创建</li><li>在下一次重新渲染时，useState返回给我们当前的state</li><li>如果每次都创建新的变量，那它就不是state了</li><li>这也是Hook的名字总是以“use”开头的原因</li></ul></li></ul><h2 id="useeffect" tabindex="-1">useEffect <a class="header-anchor" href="#useeffect" aria-label="Permalink to &quot;useEffect&quot;">​</a></h2><p><code>useEffect</code>这个Hook可以帮我们处理一些副作用，<strong>每次组件渲染完成后</strong>，React会自动帮我们调用这些副作用</p><ul><li><p>网络请求/手动更新DOM/事件监听</p></li><li><p>完成上述这些功能的Hook被称为 Effect Hook</p></li><li><p>通过<code>useEffect</code>，可以告诉React需要在组件渲染完成后执行哪些副作用</p></li><li><p>这里的<em>组件重新渲染</em>，指的是组件对应的<strong>DOM更新完毕后</strong>，回调这些副作用函数</p></li><li><p>默认情况下，无论是第一次渲染之后，还是每次更新之后，都会执行这个副作用函数</p></li></ul><p>以下面的代码为例，我们希望每次对状态<code>title</code>进行修改后，都能反映到当前页面的标题上</p><p>如果我们将<code>document.title = title</code>放到函数顶层执行，那么</p><div class="language-tsx line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">tsx</span><pre class="shiki material-theme-palenight"><code><span class="line"><span style="color:#676E95;font-style:italic;">// TitleChanger.jsx</span></span>
<span class="line"><span style="color:#89DDFF;font-style:italic;">import</span><span style="color:#A6ACCD;"> React</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">useEffect</span><span style="color:#89DDFF;">,</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">useState</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">}</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;font-style:italic;">from</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">react</span><span style="color:#89DDFF;">&#39;</span></span>
<span class="line"></span>
<span class="line"><span style="color:#89DDFF;font-style:italic;">export</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;font-style:italic;">default</span><span style="color:#A6ACCD;"> </span><span style="color:#C792EA;">function</span><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">TitleChanger</span><span style="color:#89DDFF;">()</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#C792EA;">const</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">[</span><span style="color:#A6ACCD;">title</span><span style="color:#89DDFF;">,</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">setTitle</span><span style="color:#89DDFF;">]</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">=</span><span style="color:#F07178;"> </span><span style="color:#82AAFF;">useState</span><span style="color:#F07178;">(</span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">Title</span><span style="color:#89DDFF;">&#39;</span><span style="color:#F07178;">)</span></span>
<span class="line"></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#82AAFF;">useEffect</span><span style="color:#F07178;">(</span><span style="color:#89DDFF;">()</span><span style="color:#F07178;"> </span><span style="color:#C792EA;">=&gt;</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">document</span><span style="color:#89DDFF;">.</span><span style="color:#A6ACCD;">title</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">=</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">title</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">}</span><span style="color:#F07178;">)</span></span>
<span class="line"></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;font-style:italic;">return</span><span style="color:#F07178;"> (</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">&lt;</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&lt;</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span><span style="color:#A6ACCD;">Title: </span><span style="color:#89DDFF;">{</span><span style="color:#A6ACCD;">title</span><span style="color:#89DDFF;">}&lt;/</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&lt;</span><span style="color:#F07178;">button</span><span style="color:#89DDFF;"> </span><span style="color:#C792EA;">onClick</span><span style="color:#89DDFF;">={()</span><span style="color:#A6ACCD;"> </span><span style="color:#C792EA;">=&gt;</span><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">setTitle</span><span style="color:#A6ACCD;">(</span><span style="color:#89DDFF;">new</span><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">Date</span><span style="color:#A6ACCD;">()</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">getTime</span><span style="color:#A6ACCD;">())</span><span style="color:#89DDFF;">}&gt;</span><span style="color:#A6ACCD;">Change Title</span><span style="color:#89DDFF;">&lt;/</span><span style="color:#F07178;">button</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&lt;/</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#F07178;"> )</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br><span class="line-number">17</span><br></div></div><h3 id="清理副作用" tabindex="-1">清理副作用 <a class="header-anchor" href="#清理副作用" aria-label="Permalink to &quot;清理副作用&quot;">​</a></h3><p>使用useEffect可以帮我们在组件执行重新渲染后添加额外的副作用，那怎样清理这些副作用呢？</p><ul><li>例如，我们使用<code>useEffect</code>添加了事件监听回调的副作用</li><li>当组件被卸载时，需要对事件监听回调执行清理</li><li><code>addEventListener &lt;=&gt; removeEventListener</code></li></ul><p>传入useEffect的函数的返回值是一个函数，组件被重新渲染或组件被卸载时，React会调用这个函数</p><p>我们可以借助这个功能来完成清理副作用的操作</p><p>下面的案例展示了一个输入框，当焦点处于输入框时，按下ESC键时会对输入框进行清空并使其失焦：</p><div class="language-tsx line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">tsx</span><pre class="shiki material-theme-palenight"><code><span class="line"><span style="color:#676E95;font-style:italic;">// KeydownListener.jsx</span></span>
<span class="line"><span style="color:#89DDFF;font-style:italic;">import</span><span style="color:#A6ACCD;"> React</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">useEffect</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">}</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;font-style:italic;">from</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">react</span><span style="color:#89DDFF;">&#39;</span></span>
<span class="line"></span>
<span class="line"><span style="color:#89DDFF;font-style:italic;">export</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;font-style:italic;">default</span><span style="color:#A6ACCD;"> </span><span style="color:#C792EA;">function</span><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">KeydownListener</span><span style="color:#89DDFF;">()</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#C792EA;">const</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">handleKeydown</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">=</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">(</span><span style="color:#A6ACCD;font-style:italic;">e</span><span style="color:#89DDFF;">)</span><span style="color:#F07178;"> </span><span style="color:#C792EA;">=&gt;</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;font-style:italic;">if</span><span style="color:#F07178;"> (</span><span style="color:#A6ACCD;">e</span><span style="color:#89DDFF;">.</span><span style="color:#A6ACCD;">key</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">===</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">Escape</span><span style="color:#89DDFF;">&#39;</span><span style="color:#F07178;">) </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">e</span><span style="color:#89DDFF;">.</span><span style="color:#A6ACCD;">target</span><span style="color:#89DDFF;">.</span><span style="color:#A6ACCD;">value</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">=</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">&#39;&#39;</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">e</span><span style="color:#89DDFF;">.</span><span style="color:#A6ACCD;">target</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">blur</span><span style="color:#F07178;">()</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">console</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">log</span><span style="color:#F07178;">(</span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">Escape Pressed</span><span style="color:#89DDFF;">&#39;</span><span style="color:#F07178;">)</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">}</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">}</span></span>
<span class="line"></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#82AAFF;">useEffect</span><span style="color:#F07178;">(</span><span style="color:#89DDFF;">()</span><span style="color:#F07178;"> </span><span style="color:#C792EA;">=&gt;</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#C792EA;">const</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">input</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">=</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">document</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">querySelector</span><span style="color:#F07178;">(</span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">input</span><span style="color:#89DDFF;">&#39;</span><span style="color:#F07178;">)</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">input</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">addEventListener</span><span style="color:#F07178;">(</span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">keydown</span><span style="color:#89DDFF;">&#39;</span><span style="color:#89DDFF;">,</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">handleKeydown</span><span style="color:#F07178;">)</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">console</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">log</span><span style="color:#F07178;">(</span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">Effect Ran</span><span style="color:#89DDFF;">&#39;</span><span style="color:#F07178;">)</span></span>
<span class="line"></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;font-style:italic;">return</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">()</span><span style="color:#F07178;"> </span><span style="color:#C792EA;">=&gt;</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">input</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">removeEventListener</span><span style="color:#F07178;">(</span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">keydown</span><span style="color:#89DDFF;">&#39;</span><span style="color:#89DDFF;">,</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">handleKeydown</span><span style="color:#F07178;">)</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">console</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">log</span><span style="color:#F07178;">(</span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">Effect Cleaned Up</span><span style="color:#89DDFF;">&#39;</span><span style="color:#F07178;">)</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">}</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">}</span><span style="color:#F07178;">)</span></span>
<span class="line"></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;font-style:italic;">return</span><span style="color:#F07178;"> (</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">&lt;</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&lt;</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span><span style="color:#A6ACCD;">document</span><span style="color:#89DDFF;">&lt;/</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&lt;</span><span style="color:#F07178;">input</span><span style="color:#89DDFF;"> </span><span style="color:#C792EA;">type</span><span style="color:#89DDFF;">=</span><span style="color:#89DDFF;">&quot;</span><span style="color:#C3E88D;">text</span><span style="color:#89DDFF;">&quot;</span><span style="color:#89DDFF;"> /&gt;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&lt;/</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#F07178;"> )</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br><span class="line-number">17</span><br><span class="line-number">18</span><br><span class="line-number">19</span><br><span class="line-number">20</span><br><span class="line-number">21</span><br><span class="line-number">22</span><br><span class="line-number">23</span><br><span class="line-number">24</span><br><span class="line-number">25</span><br><span class="line-number">26</span><br><span class="line-number">27</span><br><span class="line-number">28</span><br><span class="line-number">29</span><br><span class="line-number">30</span><br></div></div><p>为什么要在effect中返回一个函数？</p><ul><li>这时effect可选的清除机制，每个effect都可以返回一个清除函数</li><li>如此可以将添加和移除订阅的逻辑放在一起</li><li>它们都属于effect的一部分</li></ul><p>如果我们有较为复杂的逻辑，我们也可以在同一个组件中使用多个useEffect，并分别在不同的回调函数中返回清理副作用函数</p><h3 id="effect性能优化" tabindex="-1">Effect性能优化 <a class="header-anchor" href="#effect性能优化" aria-label="Permalink to &quot;Effect性能优化&quot;">​</a></h3><p>同时，我们也会发现一些问题，尽管我们保证了监听回调是时刻唯一、不会冗余的</p><p>但是组件每次重新渲染都会：先删除原来事件监听回调，再添加新的监听回调，这造成了额外的性能浪费</p><p>我们可以对此进行额外的优化</p><ul><li><code>useEffect</code>实际上有两个参数 <ul><li>参数一：函数，组件重新渲染时执行的回调函数</li><li>参数二：数组，回调函数在那些state发生变化时，才重新执行</li></ul></li></ul><p>默认情况下，如果不传第二个参数，没有指定更新依赖项，则只要组件重新渲染，Effect都会重新执行</p><p>如果我们为第二个参数传递一个空数组，则证明：此Effect没有依赖state，仅在首次渲染时被回调</p><div class="language-tsx line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">tsx</span><pre class="shiki material-theme-palenight has-highlighted-lines"><code><span class="line"><span style="color:#676E95;font-style:italic;">// KeydownListener.jsx</span></span>
<span class="line"><span style="color:#89DDFF;">...</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">useEffect</span><span style="color:#A6ACCD;">(</span><span style="color:#89DDFF;">()</span><span style="color:#A6ACCD;"> </span><span style="color:#C792EA;">=&gt;</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#C792EA;">const</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">input</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">=</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">document</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">querySelector</span><span style="color:#F07178;">(</span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">input</span><span style="color:#89DDFF;">&#39;</span><span style="color:#F07178;">)</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">input</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">addEventListener</span><span style="color:#F07178;">(</span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">keydown</span><span style="color:#89DDFF;">&#39;</span><span style="color:#89DDFF;">,</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">handleKeydown</span><span style="color:#F07178;">)</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">console</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">log</span><span style="color:#F07178;">(</span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">Effect Ran</span><span style="color:#89DDFF;">&#39;</span><span style="color:#F07178;">)</span></span>
<span class="line"></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;font-style:italic;">return</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">()</span><span style="color:#F07178;"> </span><span style="color:#C792EA;">=&gt;</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">input</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">removeEventListener</span><span style="color:#F07178;">(</span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">keydown</span><span style="color:#89DDFF;">&#39;</span><span style="color:#89DDFF;">,</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">handleKeydown</span><span style="color:#F07178;">)</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">console</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">log</span><span style="color:#F07178;">(</span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">Effect Cleaned Up</span><span style="color:#89DDFF;">&#39;</span><span style="color:#F07178;">)</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">}</span></span>
<span class="line highlighted"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">},</span><span style="color:#A6ACCD;"> [])</span></span>
<span class="line"><span style="color:#89DDFF;">...</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br></div></div><h2 id="usecontext" tabindex="-1">useContext <a class="header-anchor" href="#usecontext" aria-label="Permalink to &quot;useContext&quot;">​</a></h2><p>在之前的开发中，要在组件中使用共享的Context有两种方式</p><ul><li>类组件可以通过<code>ClassName.contextType = SomeContext</code>绑定上下文</li><li>在类的函数中通过<code>this.context.xxx</code>获取上下文中共享的状态</li><li>同时有多个Context时/函数式组件中，通过<code>SomeContext.Consumer</code>的方式共享上下文状态</li></ul><p>其中最大的问题就是：多个Context在同时使用时会引入大量的嵌套，而<code>useContext</code>可以帮我们解决这个问题</p><p>通过<code>useContext</code>可以直接获取到某个上下文中共享的状态变量</p><div class="vp-code-group"><div class="tabs"><input type="radio" name="group-nmnbs" id="tab-pl3deuR" checked="checked"><label for="tab-pl3deuR">Profile.jsx</label><input type="radio" name="group-nmnbs" id="tab-0Hv0Bsv"><label for="tab-0Hv0Bsv">index.js</label><input type="radio" name="group-nmnbs" id="tab-I6pZW1g"><label for="tab-I6pZW1g">App.jsx</label></div><div class="blocks"><div class="language-tsx active line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">tsx</span><pre class="shiki material-theme-palenight"><code><span class="line"><span style="color:#676E95;font-style:italic;">// Profile.jsx</span></span>
<span class="line"><span style="color:#89DDFF;font-style:italic;">import</span><span style="color:#A6ACCD;"> React</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">useContext</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">}</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;font-style:italic;">from</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">react</span><span style="color:#89DDFF;">&#39;</span></span>
<span class="line"><span style="color:#89DDFF;font-style:italic;">import</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">UserContext</span><span style="color:#89DDFF;">,</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">ThemeContext</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">}</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;font-style:italic;">from</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">../context</span><span style="color:#89DDFF;">&#39;</span></span>
<span class="line"></span>
<span class="line"><span style="color:#89DDFF;font-style:italic;">export</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;font-style:italic;">default</span><span style="color:#A6ACCD;"> </span><span style="color:#C792EA;">function</span><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">Profile</span><span style="color:#89DDFF;">()</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#C792EA;">const</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">userContext</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">=</span><span style="color:#F07178;"> </span><span style="color:#82AAFF;">useContext</span><span style="color:#F07178;">(</span><span style="color:#A6ACCD;">UserContext</span><span style="color:#F07178;">)</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#C792EA;">const</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">themeContext</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">=</span><span style="color:#F07178;"> </span><span style="color:#82AAFF;">useContext</span><span style="color:#F07178;">(</span><span style="color:#A6ACCD;">ThemeContext</span><span style="color:#F07178;">)</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;font-style:italic;">return</span><span style="color:#F07178;"> (</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">&lt;</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&lt;</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span><span style="color:#A6ACCD;">Profile</span><span style="color:#89DDFF;">&lt;/</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&lt;</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span><span style="color:#A6ACCD;">userName: </span><span style="color:#89DDFF;">{</span><span style="color:#A6ACCD;">userContext</span><span style="color:#89DDFF;">.</span><span style="color:#A6ACCD;">userName</span><span style="color:#89DDFF;">}&lt;/</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&lt;</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span><span style="color:#A6ACCD;">age: </span><span style="color:#89DDFF;">{</span><span style="color:#A6ACCD;">userContext</span><span style="color:#89DDFF;">.</span><span style="color:#A6ACCD;">age</span><span style="color:#89DDFF;">}&lt;/</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&lt;</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span><span style="color:#A6ACCD;">theme: </span><span style="color:#89DDFF;">{</span><span style="color:#A6ACCD;">themeContext</span><span style="color:#89DDFF;">.</span><span style="color:#A6ACCD;">theme</span><span style="color:#89DDFF;">}&lt;/</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&lt;/</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#F07178;"> )</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br></div></div><div class="language-tsx line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">tsx</span><pre class="shiki material-theme-palenight"><code><span class="line"><span style="color:#676E95;font-style:italic;">// context/index.js</span></span>
<span class="line"><span style="color:#89DDFF;font-style:italic;">import</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">createContext</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">}</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;font-style:italic;">from</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">react</span><span style="color:#89DDFF;">&#39;</span></span>
<span class="line"></span>
<span class="line"><span style="color:#89DDFF;font-style:italic;">export</span><span style="color:#A6ACCD;"> </span><span style="color:#C792EA;">const</span><span style="color:#A6ACCD;"> UserContext </span><span style="color:#89DDFF;">=</span><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">createContext</span><span style="color:#A6ACCD;">(</span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#F07178;">userName</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&#39;&#39;</span><span style="color:#89DDFF;">,</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#F07178;">userAge</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">0</span></span>
<span class="line"><span style="color:#89DDFF;">}</span><span style="color:#A6ACCD;">)</span></span>
<span class="line"></span>
<span class="line"><span style="color:#89DDFF;font-style:italic;">export</span><span style="color:#A6ACCD;"> </span><span style="color:#C792EA;">const</span><span style="color:#A6ACCD;"> ThemeContext </span><span style="color:#89DDFF;">=</span><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">createContext</span><span style="color:#A6ACCD;">(</span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#F07178;">theme</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">light</span><span style="color:#89DDFF;">&#39;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span><span style="color:#A6ACCD;">)</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br></div></div><div class="language-tsx line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">tsx</span><pre class="shiki material-theme-palenight"><code><span class="line"><span style="color:#676E95;font-style:italic;">// App.jsx</span></span>
<span class="line"><span style="color:#89DDFF;font-style:italic;">import</span><span style="color:#A6ACCD;"> React </span><span style="color:#89DDFF;font-style:italic;">from</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">react</span><span style="color:#89DDFF;">&#39;</span></span>
<span class="line"><span style="color:#89DDFF;font-style:italic;">import</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">UserContext</span><span style="color:#89DDFF;">,</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">ThemeContext</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">}</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;font-style:italic;">from</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">./context</span><span style="color:#89DDFF;">&#39;</span></span>
<span class="line"><span style="color:#89DDFF;font-style:italic;">import</span><span style="color:#A6ACCD;"> Profile </span><span style="color:#89DDFF;font-style:italic;">from</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">./components/Profile</span><span style="color:#89DDFF;">&#39;</span></span>
<span class="line"></span>
<span class="line"><span style="color:#89DDFF;font-style:italic;">export</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;font-style:italic;">default</span><span style="color:#A6ACCD;"> </span><span style="color:#C792EA;">function</span><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">App</span><span style="color:#89DDFF;">()</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;font-style:italic;">return</span><span style="color:#F07178;"> (</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">&lt;</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&lt;</span><span style="color:#FFCB6B;">UserContext.Provider</span><span style="color:#89DDFF;"> </span><span style="color:#C792EA;">value</span><span style="color:#89DDFF;">={{</span><span style="color:#A6ACCD;"> </span><span style="color:#F07178;">userName</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">Ziu</span><span style="color:#89DDFF;">&#39;</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#F07178;">age</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">18</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">}}&gt;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&lt;</span><span style="color:#FFCB6B;">ThemeContext.Provider</span><span style="color:#89DDFF;"> </span><span style="color:#C792EA;">value</span><span style="color:#89DDFF;">={{</span><span style="color:#A6ACCD;"> </span><span style="color:#F07178;">theme</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">dark</span><span style="color:#89DDFF;">&#39;</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">}}&gt;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&lt;</span><span style="color:#FFCB6B;">Profile</span><span style="color:#89DDFF;"> /&gt;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&lt;/</span><span style="color:#FFCB6B;">ThemeContext.Provider</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&lt;/</span><span style="color:#FFCB6B;">UserContext.Provider</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&lt;/</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#F07178;"> )</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br></div></div></div></div><p>当组件上层最近的<code>SomeContext.Provider</code>提供的值发生更新时，<code>useContext</code>会使用上下文中最新的数据触发组件的重新渲染</p><h2 id="usereducer" tabindex="-1">useReducer <a class="header-anchor" href="#usereducer" aria-label="Permalink to &quot;useReducer&quot;">​</a></h2><p><code>useReducer</code>并不是Redux的替代品</p><ul><li><code>useReducer</code>是<code>useState</code>在某些场景下的替代方案</li><li>如果state需要处理的<strong>数据较为复杂</strong>，我们可以通过<code>useReducer</code>对其进行拆分</li><li>或者需要修改的state需要依赖之前的state时，也可以使用<code>useReducer</code></li></ul><p>下面举一个例子：用户信息包含多个复杂的字段，当用户执行操作后需要同时对多个字段进行修改</p><p>我们分别用<code>useState</code>和<code>useReducer</code>来实现：</p><div class="vp-code-group"><div class="tabs"><input type="radio" name="group-DviCi" id="tab-zxIeePW" checked="checked"><label for="tab-zxIeePW">UserInfoWithReducer.jsx</label><input type="radio" name="group-DviCi" id="tab-MyI7wUu"><label for="tab-MyI7wUu">UserInfo.jsx</label></div><div class="blocks"><div class="language-tsx active line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">tsx</span><pre class="shiki material-theme-palenight"><code><span class="line"><span style="color:#676E95;font-style:italic;">// UserInfoWithReducer.jsx</span></span>
<span class="line"><span style="color:#89DDFF;font-style:italic;">import</span><span style="color:#A6ACCD;"> React</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">useReducer</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">}</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;font-style:italic;">from</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">react</span><span style="color:#89DDFF;">&#39;</span></span>
<span class="line"></span>
<span class="line"><span style="color:#C792EA;">function</span><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">reducer</span><span style="color:#89DDFF;">(</span><span style="color:#A6ACCD;font-style:italic;">state</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#A6ACCD;font-style:italic;">action</span><span style="color:#89DDFF;">)</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;font-style:italic;">switch</span><span style="color:#F07178;"> (</span><span style="color:#A6ACCD;">action</span><span style="color:#89DDFF;">.</span><span style="color:#A6ACCD;">type</span><span style="color:#F07178;">) </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;font-style:italic;">case</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">addAge</span><span style="color:#89DDFF;">&#39;</span><span style="color:#89DDFF;">:</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;font-style:italic;">return</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">...</span><span style="color:#A6ACCD;">state</span><span style="color:#89DDFF;">,</span></span>
<span class="line"><span style="color:#F07178;"> age</span><span style="color:#89DDFF;">:</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">state</span><span style="color:#89DDFF;">.</span><span style="color:#A6ACCD;">age</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">+</span><span style="color:#F07178;"> </span><span style="color:#F78C6C;">1</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">}</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;font-style:italic;">case</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">pushLikes</span><span style="color:#89DDFF;">&#39;</span><span style="color:#89DDFF;">:</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;font-style:italic;">return</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">...</span><span style="color:#A6ACCD;">state</span><span style="color:#89DDFF;">,</span></span>
<span class="line"><span style="color:#F07178;"> likes</span><span style="color:#89DDFF;">:</span><span style="color:#F07178;"> [</span><span style="color:#89DDFF;">...</span><span style="color:#A6ACCD;">state</span><span style="color:#89DDFF;">.</span><span style="color:#A6ACCD;">likes</span><span style="color:#89DDFF;">,</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">action</span><span style="color:#89DDFF;">.</span><span style="color:#A6ACCD;">payload</span><span style="color:#F07178;">]</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">}</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;font-style:italic;">case</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">modifyName</span><span style="color:#89DDFF;">&#39;</span><span style="color:#89DDFF;">:</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;font-style:italic;">return</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">...</span><span style="color:#A6ACCD;">state</span><span style="color:#89DDFF;">,</span></span>
<span class="line"><span style="color:#F07178;"> name</span><span style="color:#89DDFF;">:</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">action</span><span style="color:#89DDFF;">.</span><span style="color:#A6ACCD;">payload</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">}</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;font-style:italic;">default</span><span style="color:#89DDFF;">:</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;font-style:italic;">return</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">state</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">}</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span>
<span class="line"><span style="color:#89DDFF;font-style:italic;">export</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;font-style:italic;">default</span><span style="color:#A6ACCD;"> </span><span style="color:#C792EA;">function</span><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">UserInfoWithReducer</span><span style="color:#89DDFF;">()</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#C792EA;">const</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">[</span><span style="color:#A6ACCD;">userInfo</span><span style="color:#89DDFF;">,</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">dispatch</span><span style="color:#89DDFF;">]</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">=</span><span style="color:#F07178;"> </span><span style="color:#82AAFF;">useReducer</span><span style="color:#F07178;">(</span><span style="color:#A6ACCD;">reducer</span><span style="color:#89DDFF;">,</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> id</span><span style="color:#89DDFF;">:</span><span style="color:#F07178;"> </span><span style="color:#F78C6C;">1</span><span style="color:#89DDFF;">,</span></span>
<span class="line"><span style="color:#F07178;"> name</span><span style="color:#89DDFF;">:</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">Ziu</span><span style="color:#89DDFF;">&#39;</span><span style="color:#89DDFF;">,</span></span>
<span class="line"><span style="color:#F07178;"> age</span><span style="color:#89DDFF;">:</span><span style="color:#F07178;"> </span><span style="color:#F78C6C;">18</span><span style="color:#89DDFF;">,</span></span>
<span class="line"><span style="color:#F07178;"> likes</span><span style="color:#89DDFF;">:</span><span style="color:#F07178;"> [</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">{</span><span style="color:#F07178;"> id</span><span style="color:#89DDFF;">:</span><span style="color:#F07178;"> </span><span style="color:#F78C6C;">5</span><span style="color:#89DDFF;">,</span><span style="color:#F07178;"> name</span><span style="color:#89DDFF;">:</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">Why</span><span style="color:#89DDFF;">&#39;</span><span style="color:#89DDFF;">,</span><span style="color:#F07178;"> age</span><span style="color:#89DDFF;">:</span><span style="color:#F07178;"> </span><span style="color:#F78C6C;">19</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">},</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">{</span><span style="color:#F07178;"> id</span><span style="color:#89DDFF;">:</span><span style="color:#F07178;"> </span><span style="color:#F78C6C;">8</span><span style="color:#89DDFF;">,</span><span style="color:#F07178;"> name</span><span style="color:#89DDFF;">:</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">ZIU</span><span style="color:#89DDFF;">&#39;</span><span style="color:#89DDFF;">,</span><span style="color:#F07178;"> age</span><span style="color:#89DDFF;">:</span><span style="color:#F07178;"> </span><span style="color:#F78C6C;">20</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">}</span></span>
<span class="line"><span style="color:#F07178;"> ]</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">}</span><span style="color:#F07178;">)</span></span>
<span class="line"></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#C792EA;">const</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">addAge</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">=</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">()</span><span style="color:#F07178;"> </span><span style="color:#C792EA;">=&gt;</span><span style="color:#F07178;"> </span><span style="color:#82AAFF;">dispatch</span><span style="color:#F07178;">(</span><span style="color:#89DDFF;">{</span><span style="color:#F07178;"> type</span><span style="color:#89DDFF;">:</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">addAge</span><span style="color:#89DDFF;">&#39;</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">}</span><span style="color:#F07178;">)</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#C792EA;">const</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">pushLikes</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">=</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">(</span><span style="color:#A6ACCD;font-style:italic;">user</span><span style="color:#89DDFF;">)</span><span style="color:#F07178;"> </span><span style="color:#C792EA;">=&gt;</span><span style="color:#F07178;"> </span><span style="color:#82AAFF;">dispatch</span><span style="color:#F07178;">(</span><span style="color:#89DDFF;">{</span><span style="color:#F07178;"> type</span><span style="color:#89DDFF;">:</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">pushLikes</span><span style="color:#89DDFF;">&#39;</span><span style="color:#89DDFF;">,</span><span style="color:#F07178;"> payload</span><span style="color:#89DDFF;">:</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">user</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">}</span><span style="color:#F07178;">)</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#C792EA;">const</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">modifyName</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">=</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">(</span><span style="color:#A6ACCD;font-style:italic;">name</span><span style="color:#89DDFF;">)</span><span style="color:#F07178;"> </span><span style="color:#C792EA;">=&gt;</span><span style="color:#F07178;"> </span><span style="color:#82AAFF;">dispatch</span><span style="color:#F07178;">(</span><span style="color:#89DDFF;">{</span><span style="color:#F07178;"> type</span><span style="color:#89DDFF;">:</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">modifyName</span><span style="color:#89DDFF;">&#39;</span><span style="color:#89DDFF;">,</span><span style="color:#F07178;"> payload</span><span style="color:#89DDFF;">:</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">name</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">}</span><span style="color:#F07178;">)</span></span>
<span class="line"></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;font-style:italic;">return</span><span style="color:#F07178;"> (</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">&lt;</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&lt;</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span><span style="color:#A6ACCD;">UserInfoWithReducer</span><span style="color:#89DDFF;">&lt;/</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&lt;</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;{</span><span style="color:#A6ACCD;">JSON</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">stringify</span><span style="color:#A6ACCD;">(userInfo)</span><span style="color:#89DDFF;">}&lt;/</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&lt;</span><span style="color:#F07178;">button</span><span style="color:#89DDFF;"> </span><span style="color:#C792EA;">onClick</span><span style="color:#89DDFF;">={</span><span style="color:#A6ACCD;">addAge</span><span style="color:#89DDFF;">}&gt;</span><span style="color:#A6ACCD;">Add Age</span><span style="color:#89DDFF;">&lt;/</span><span style="color:#F07178;">button</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&lt;</span><span style="color:#F07178;">button</span><span style="color:#89DDFF;"> </span><span style="color:#C792EA;">onClick</span><span style="color:#89DDFF;">={()</span><span style="color:#A6ACCD;"> </span><span style="color:#C792EA;">=&gt;</span><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">pushLikes</span><span style="color:#A6ACCD;">(</span><span style="color:#89DDFF;">{</span><span style="color:#A6ACCD;"> </span><span style="color:#F07178;">id</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">10</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#F07178;">name</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">ZiuChen</span><span style="color:#89DDFF;">&#39;</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#F07178;">age</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">21</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">}</span><span style="color:#A6ACCD;">)</span><span style="color:#89DDFF;">}&gt;</span><span style="color:#A6ACCD;">Push Likes</span><span style="color:#89DDFF;">&lt;/</span><span style="color:#F07178;">button</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&lt;</span><span style="color:#F07178;">button</span><span style="color:#89DDFF;"> </span><span style="color:#C792EA;">onClick</span><span style="color:#89DDFF;">={()</span><span style="color:#A6ACCD;"> </span><span style="color:#C792EA;">=&gt;</span><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">modifyName</span><span style="color:#A6ACCD;">(</span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">ZiuChen</span><span style="color:#89DDFF;">&#39;</span><span style="color:#A6ACCD;">)</span><span style="color:#89DDFF;">}&gt;</span><span style="color:#A6ACCD;">Modify Name</span><span style="color:#89DDFF;">&lt;/</span><span style="color:#F07178;">button</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&lt;/</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#F07178;"> )</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br><span class="line-number">17</span><br><span class="line-number">18</span><br><span class="line-number">19</span><br><span class="line-number">20</span><br><span class="line-number">21</span><br><span class="line-number">22</span><br><span class="line-number">23</span><br><span class="line-number">24</span><br><span class="line-number">25</span><br><span class="line-number">26</span><br><span class="line-number">27</span><br><span class="line-number">28</span><br><span class="line-number">29</span><br><span class="line-number">30</span><br><span class="line-number">31</span><br><span class="line-number">32</span><br><span class="line-number">33</span><br><span class="line-number">34</span><br><span class="line-number">35</span><br><span class="line-number">36</span><br><span class="line-number">37</span><br><span class="line-number">38</span><br><span class="line-number">39</span><br><span class="line-number">40</span><br><span class="line-number">41</span><br><span class="line-number">42</span><br><span class="line-number">43</span><br><span class="line-number">44</span><br><span class="line-number">45</span><br><span class="line-number">46</span><br><span class="line-number">47</span><br><span class="line-number">48</span><br><span class="line-number">49</span><br><span class="line-number">50</span><br></div></div><div class="language-tsx line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">tsx</span><pre class="shiki material-theme-palenight"><code><span class="line"><span style="color:#676E95;font-style:italic;">// UserInfo.jsx</span></span>
<span class="line"><span style="color:#89DDFF;font-style:italic;">import</span><span style="color:#A6ACCD;"> React</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">useState</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">}</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;font-style:italic;">from</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">react</span><span style="color:#89DDFF;">&#39;</span></span>
<span class="line"></span>
<span class="line"><span style="color:#89DDFF;font-style:italic;">export</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;font-style:italic;">default</span><span style="color:#A6ACCD;"> </span><span style="color:#C792EA;">function</span><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">UserInfo</span><span style="color:#89DDFF;">()</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#C792EA;">const</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">[</span><span style="color:#A6ACCD;">userInfo</span><span style="color:#89DDFF;">,</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">setUserInfo</span><span style="color:#89DDFF;">]</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">=</span><span style="color:#F07178;"> </span><span style="color:#82AAFF;">useState</span><span style="color:#F07178;">(</span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> id</span><span style="color:#89DDFF;">:</span><span style="color:#F07178;"> </span><span style="color:#F78C6C;">1</span><span style="color:#89DDFF;">,</span></span>
<span class="line"><span style="color:#F07178;"> name</span><span style="color:#89DDFF;">:</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">Ziu</span><span style="color:#89DDFF;">&#39;</span><span style="color:#89DDFF;">,</span></span>
<span class="line"><span style="color:#F07178;"> age</span><span style="color:#89DDFF;">:</span><span style="color:#F07178;"> </span><span style="color:#F78C6C;">18</span><span style="color:#89DDFF;">,</span></span>
<span class="line"><span style="color:#F07178;"> likes</span><span style="color:#89DDFF;">:</span><span style="color:#F07178;"> [</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">{</span><span style="color:#F07178;"> id</span><span style="color:#89DDFF;">:</span><span style="color:#F07178;"> </span><span style="color:#F78C6C;">5</span><span style="color:#89DDFF;">,</span><span style="color:#F07178;"> name</span><span style="color:#89DDFF;">:</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">Why</span><span style="color:#89DDFF;">&#39;</span><span style="color:#89DDFF;">,</span><span style="color:#F07178;"> age</span><span style="color:#89DDFF;">:</span><span style="color:#F07178;"> </span><span style="color:#F78C6C;">19</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">},</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">{</span><span style="color:#F07178;"> id</span><span style="color:#89DDFF;">:</span><span style="color:#F07178;"> </span><span style="color:#F78C6C;">8</span><span style="color:#89DDFF;">,</span><span style="color:#F07178;"> name</span><span style="color:#89DDFF;">:</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">ZIU</span><span style="color:#89DDFF;">&#39;</span><span style="color:#89DDFF;">,</span><span style="color:#F07178;"> age</span><span style="color:#89DDFF;">:</span><span style="color:#F07178;"> </span><span style="color:#F78C6C;">20</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">}</span></span>
<span class="line"><span style="color:#F07178;"> ]</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">}</span><span style="color:#F07178;">)</span></span>
<span class="line"></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#C792EA;">const</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">addAge</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">=</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">()</span><span style="color:#F07178;"> </span><span style="color:#C792EA;">=&gt;</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#82AAFF;">setUserInfo</span><span style="color:#F07178;">(</span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">...</span><span style="color:#A6ACCD;">userInfo</span><span style="color:#89DDFF;">,</span></span>
<span class="line"><span style="color:#F07178;"> age</span><span style="color:#89DDFF;">:</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">userInfo</span><span style="color:#89DDFF;">.</span><span style="color:#A6ACCD;">age</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">+</span><span style="color:#F07178;"> </span><span style="color:#F78C6C;">1</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">}</span><span style="color:#F07178;">)</span></span>
<span class="line"></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#C792EA;">const</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">pushLikes</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">=</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">(</span><span style="color:#A6ACCD;font-style:italic;">user</span><span style="color:#89DDFF;">)</span><span style="color:#F07178;"> </span><span style="color:#C792EA;">=&gt;</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#82AAFF;">setUserInfo</span><span style="color:#F07178;">(</span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">...</span><span style="color:#A6ACCD;">userInfo</span><span style="color:#89DDFF;">,</span></span>
<span class="line"><span style="color:#F07178;"> likes</span><span style="color:#89DDFF;">:</span><span style="color:#F07178;"> [</span><span style="color:#89DDFF;">...</span><span style="color:#A6ACCD;">userInfo</span><span style="color:#89DDFF;">.</span><span style="color:#A6ACCD;">likes</span><span style="color:#89DDFF;">,</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">user</span><span style="color:#F07178;">]</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">}</span><span style="color:#F07178;">)</span></span>
<span class="line"></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#C792EA;">const</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">modifyName</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">=</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">(</span><span style="color:#A6ACCD;font-style:italic;">name</span><span style="color:#89DDFF;">)</span><span style="color:#F07178;"> </span><span style="color:#C792EA;">=&gt;</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#82AAFF;">setUserInfo</span><span style="color:#F07178;">(</span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">...</span><span style="color:#A6ACCD;">userInfo</span><span style="color:#89DDFF;">,</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">name</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">}</span><span style="color:#F07178;">)</span></span>
<span class="line"></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;font-style:italic;">return</span><span style="color:#F07178;"> (</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">&lt;</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&lt;</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span><span style="color:#A6ACCD;">UserInfo</span><span style="color:#89DDFF;">&lt;/</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&lt;</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;{</span><span style="color:#A6ACCD;">JSON</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">stringify</span><span style="color:#A6ACCD;">(userInfo)</span><span style="color:#89DDFF;">}&lt;/</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&lt;</span><span style="color:#F07178;">button</span><span style="color:#89DDFF;"> </span><span style="color:#C792EA;">onClick</span><span style="color:#89DDFF;">={()</span><span style="color:#A6ACCD;"> </span><span style="color:#C792EA;">=&gt;</span><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">addAge</span><span style="color:#A6ACCD;">()</span><span style="color:#89DDFF;">}&gt;</span><span style="color:#A6ACCD;">Add Age</span><span style="color:#89DDFF;">&lt;/</span><span style="color:#F07178;">button</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&lt;</span><span style="color:#F07178;">button</span><span style="color:#89DDFF;"> </span><span style="color:#C792EA;">onClick</span><span style="color:#89DDFF;">={()</span><span style="color:#A6ACCD;"> </span><span style="color:#C792EA;">=&gt;</span><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">pushLikes</span><span style="color:#A6ACCD;">(</span><span style="color:#89DDFF;">{</span><span style="color:#A6ACCD;"> </span><span style="color:#F07178;">id</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">10</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#F07178;">name</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">ZiuChen</span><span style="color:#89DDFF;">&#39;</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#F07178;">age</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">21</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">}</span><span style="color:#A6ACCD;">)</span><span style="color:#89DDFF;">}&gt;</span><span style="color:#A6ACCD;">Push Likes</span><span style="color:#89DDFF;">&lt;/</span><span style="color:#F07178;">button</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&lt;</span><span style="color:#F07178;">button</span><span style="color:#89DDFF;"> </span><span style="color:#C792EA;">onClick</span><span style="color:#89DDFF;">={()</span><span style="color:#A6ACCD;"> </span><span style="color:#C792EA;">=&gt;</span><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">modifyName</span><span style="color:#A6ACCD;">(</span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">ZiuChen</span><span style="color:#89DDFF;">&#39;</span><span style="color:#A6ACCD;">)</span><span style="color:#89DDFF;">}&gt;</span><span style="color:#A6ACCD;">Modify Name</span><span style="color:#89DDFF;">&lt;/</span><span style="color:#F07178;">button</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&lt;/</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#F07178;"> )</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br><span class="line-number">17</span><br><span class="line-number">18</span><br><span class="line-number">19</span><br><span class="line-number">20</span><br><span class="line-number">21</span><br><span class="line-number">22</span><br><span class="line-number">23</span><br><span class="line-number">24</span><br><span class="line-number">25</span><br><span class="line-number">26</span><br><span class="line-number">27</span><br><span class="line-number">28</span><br><span class="line-number">29</span><br><span class="line-number">30</span><br><span class="line-number">31</span><br><span class="line-number">32</span><br><span class="line-number">33</span><br><span class="line-number">34</span><br><span class="line-number">35</span><br><span class="line-number">36</span><br><span class="line-number">37</span><br><span class="line-number">38</span><br><span class="line-number">39</span><br><span class="line-number">40</span><br><span class="line-number">41</span><br><span class="line-number">42</span><br></div></div></div></div><p>从代码中可以看出差距：对于复杂的更新状态逻辑，使用<code>useReducer</code>可以将他们聚合在一起，通过统一的出口对状态进行更新，而不像<code>useState</code>方案中需要频繁调用暴露在外部的<code>setUserInfo</code>状态更新接口</p><p>当然，对于复杂数据的处理，也可以将其放到Redux这类的状态管理中，如果没有Redux，那么<code>useReducer</code>可以在一定程度上扮演Redux的角色，但是本质还是<code>useState</code>的替代方案</p><h2 id="usecallback和usememo" tabindex="-1">useCallback和useMemo <a class="header-anchor" href="#usecallback和usememo" aria-label="Permalink to &quot;useCallback和useMemo&quot;">​</a></h2><p>这两个Hook都是用于性能优化</p><h3 id="usecallback" tabindex="-1">useCallback <a class="header-anchor" href="#usecallback" aria-label="Permalink to &quot;useCallback&quot;">​</a></h3><p>我们以计数器案例来对<code>useCallback</code>进行说明：</p><div class="language-tsx line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">tsx</span><pre class="shiki material-theme-palenight"><code><span class="line"><span style="color:#676E95;font-style:italic;">// Counter.jsx</span></span>
<span class="line"><span style="color:#89DDFF;font-style:italic;">import</span><span style="color:#A6ACCD;"> React</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">useState</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">}</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;font-style:italic;">from</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">react</span><span style="color:#89DDFF;">&#39;</span></span>
<span class="line"></span>
<span class="line"><span style="color:#89DDFF;font-style:italic;">export</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;font-style:italic;">default</span><span style="color:#A6ACCD;"> </span><span style="color:#C792EA;">function</span><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">Counter</span><span style="color:#89DDFF;">()</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#C792EA;">const</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">[</span><span style="color:#A6ACCD;">count</span><span style="color:#89DDFF;">,</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">setCount</span><span style="color:#89DDFF;">]</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">=</span><span style="color:#F07178;"> </span><span style="color:#82AAFF;">useState</span><span style="color:#F07178;">(</span><span style="color:#F78C6C;">0</span><span style="color:#F07178;">)</span></span>
<span class="line"></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#C792EA;">function</span><span style="color:#F07178;"> </span><span style="color:#82AAFF;">increment</span><span style="color:#89DDFF;">()</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#82AAFF;">setCount</span><span style="color:#F07178;">(</span><span style="color:#A6ACCD;">count</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">+</span><span style="color:#F07178;"> </span><span style="color:#F78C6C;">1</span><span style="color:#F07178;">)</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">}</span></span>
<span class="line"></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;font-style:italic;">return</span><span style="color:#F07178;"> (</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">&lt;</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&lt;</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span><span style="color:#A6ACCD;">Counter</span><span style="color:#89DDFF;">&lt;/</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&lt;</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;{</span><span style="color:#A6ACCD;">count</span><span style="color:#89DDFF;">}&lt;/</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&lt;</span><span style="color:#F07178;">button</span><span style="color:#89DDFF;"> </span><span style="color:#C792EA;">onClick</span><span style="color:#89DDFF;">={</span><span style="color:#A6ACCD;">increment</span><span style="color:#89DDFF;">}&gt;</span><span style="color:#A6ACCD;">+1</span><span style="color:#89DDFF;">&lt;/</span><span style="color:#F07178;">button</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&lt;/</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#F07178;"> )</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br><span class="line-number">17</span><br><span class="line-number">18</span><br></div></div><p>当我们每次点击<code>+1</code>的button时，整个函数都会被重新执行一次，但是<code>increment</code>也会被重复定义，虽然上一次组件渲染快照中的<code>increment</code>函数由于引用次数为0，会被GC机制回收，但是函数的重复定义对性能也存在消耗</p><p>但是<code>useCallback</code>的使用常常存在一个误区：使用<code>useCallback</code>可以减少函数重复定义，以此来进行性能优化</p><div class="language-tsx line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">tsx</span><pre class="shiki material-theme-palenight"><code><span class="line"><span style="color:#676E95;font-style:italic;">// Counter.jsx</span></span>
<span class="line"><span style="color:#89DDFF;font-style:italic;">import</span><span style="color:#A6ACCD;"> React</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">useState</span><span style="color:#89DDFF;">,</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">useCallback</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">}</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;font-style:italic;">from</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">react</span><span style="color:#89DDFF;">&#39;</span></span>
<span class="line"></span>
<span class="line"><span style="color:#89DDFF;font-style:italic;">export</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;font-style:italic;">default</span><span style="color:#A6ACCD;"> </span><span style="color:#C792EA;">function</span><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">Counter</span><span style="color:#89DDFF;">()</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#C792EA;">const</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">[</span><span style="color:#A6ACCD;">count</span><span style="color:#89DDFF;">,</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">setCount</span><span style="color:#89DDFF;">]</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">=</span><span style="color:#F07178;"> </span><span style="color:#82AAFF;">useState</span><span style="color:#F07178;">(</span><span style="color:#F78C6C;">0</span><span style="color:#F07178;">)</span></span>
<span class="line"></span>
<span class="line"><span style="color:#89DDFF;"> </span><span style="color:#676E95;font-style:italic;">// var1 = useCallback(fn1)</span></span>
<span class="line"><span style="color:#89DDFF;"> </span><span style="color:#676E95;font-style:italic;">// var2 = useCallback(fn2)</span></span>
<span class="line"><span style="color:#89DDFF;"> </span><span style="color:#676E95;font-style:italic;">// var1 === var2 === fn0</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#C792EA;">const</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">increment</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">=</span><span style="color:#F07178;"> </span><span style="color:#82AAFF;">useCallback</span><span style="color:#F07178;">(</span><span style="color:#C792EA;">function</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">()</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#82AAFF;">setCount</span><span style="color:#F07178;">(</span><span style="color:#A6ACCD;">count</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">+</span><span style="color:#F07178;"> </span><span style="color:#F78C6C;">1</span><span style="color:#F07178;">)</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">},</span><span style="color:#F07178;"> [</span><span style="color:#A6ACCD;">count</span><span style="color:#F07178;">])</span></span>
<span class="line"></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;font-style:italic;">return</span><span style="color:#F07178;"> (</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">&lt;</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&lt;</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span><span style="color:#A6ACCD;">Counter</span><span style="color:#89DDFF;">&lt;/</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&lt;</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;{</span><span style="color:#A6ACCD;">count</span><span style="color:#89DDFF;">}&lt;/</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&lt;</span><span style="color:#F07178;">button</span><span style="color:#89DDFF;"> </span><span style="color:#C792EA;">onClick</span><span style="color:#89DDFF;">={</span><span style="color:#A6ACCD;">increment</span><span style="color:#89DDFF;">}&gt;</span><span style="color:#A6ACCD;">+1</span><span style="color:#89DDFF;">&lt;/</span><span style="color:#F07178;">button</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&lt;/</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#F07178;"> )</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br><span class="line-number">17</span><br><span class="line-number">18</span><br><span class="line-number">19</span><br><span class="line-number">20</span><br><span class="line-number">21</span><br></div></div><p>本质上，传递给<code>useCallback</code>的参数时一个函数，这个函数在每次重新渲染时也会被重新定义，所以<code>useCallback</code>并没有解决函数重新定义的问题，它只是保证了组件每次访问<code>increment</code>时，访问到的都是同一个函数引用</p><ul><li><code>useCallback</code>会返回一个函数的memoized值</li><li>在依赖不变的情况下，多次定义时，返回的值是完全相同的</li></ul><p>在使用<code>useCallback</code>时，我们同样可以为其传入一个依赖数组，仅当依赖数组中的state值发生变化时，<code>useCallback</code>才会返回一个新的函数</p><p>当我们为其传入一个空的依赖数组时，这里涉及到一个概念：闭包陷阱</p><div class="language-tsx line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">tsx</span><pre class="shiki material-theme-palenight has-highlighted-lines"><code><span class="line"><span style="color:#676E95;font-style:italic;">// Counter.jsx</span></span>
<span class="line"><span style="color:#89DDFF;">...</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#C792EA;">const</span><span style="color:#A6ACCD;"> increment </span><span style="color:#89DDFF;">=</span><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">useCallback</span><span style="color:#A6ACCD;">(</span><span style="color:#C792EA;">function</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">()</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#82AAFF;">setCount</span><span style="color:#F07178;">(</span><span style="color:#A6ACCD;">count</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">+</span><span style="color:#F07178;"> </span><span style="color:#F78C6C;">1</span><span style="color:#F07178;">)</span></span>
<span class="line highlighted"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">},</span><span style="color:#A6ACCD;"> [])</span></span>
<span class="line"><span style="color:#89DDFF;">...</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br></div></div><p>即使我们多次点击+1的按钮，状态count也不会发生变化，这是因为依赖数组为空时，<code>useCallback</code>每次返回的都是第一次定义时的函数，而那个函数的<code>count</code>值始终为0，那么每次<code>setCount</code>得到的值都为1</p><blockquote><p>闭包陷阱：函数在定义时，从上层作用域捕获变量，并保存在闭包中。</p><p>后续即使重复定义新的函数，其取到的值仍然是闭包内部保存的变量的值，而这个值是始终没有发生改变的</p></blockquote><p>这里我们使用普通函数模拟了一下这个场景</p><div class="language-js line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">js</span><pre class="shiki material-theme-palenight"><code><span class="line"><span style="color:#C792EA;">function</span><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">foo</span><span style="color:#89DDFF;">()</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#C792EA;">let</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">count</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">=</span><span style="color:#F07178;"> </span><span style="color:#F78C6C;">0</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#C792EA;">function</span><span style="color:#F07178;"> </span><span style="color:#82AAFF;">bar</span><span style="color:#89DDFF;">()</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">console</span><span style="color:#89DDFF;">.</span><span style="color:#82AAFF;">log</span><span style="color:#F07178;">(</span><span style="color:#A6ACCD;">count</span><span style="color:#F07178;"> </span><span style="color:#89DDFF;">+</span><span style="color:#F07178;"> </span><span style="color:#F78C6C;">1</span><span style="color:#F07178;">)</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;">}</span></span>
<span class="line"><span style="color:#F07178;"> </span><span style="color:#89DDFF;font-style:italic;">return</span><span style="color:#F07178;"> </span><span style="color:#A6ACCD;">bar</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span>
<span class="line"><span style="color:#C792EA;">const</span><span style="color:#A6ACCD;"> bar1 </span><span style="color:#89DDFF;">=</span><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">foo</span><span style="color:#A6ACCD;">()</span></span>
<span class="line"></span>
<span class="line"><span style="color:#82AAFF;">bar1</span><span style="color:#A6ACCD;">() </span><span style="color:#676E95;font-style:italic;">// 1</span></span>
<span class="line"><span style="color:#82AAFF;">bar1</span><span style="color:#A6ACCD;">() </span><span style="color:#676E95;font-style:italic;">// 1</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br></div></div><p>不论调用了多少次<code>bar1</code>，其内部取到的值都始终是最初的那个<code>count</code>，自然值也不会发生变化</p><p>所以，我们需要显式地为<code>useCallback</code>指定依赖state，这样才能让函数准确的使用到最新的状态</p><h3 id="真实的usecallback使用场景" tabindex="-1">真实的useCallback使用场景 <a class="header-anchor" href="#真实的usecallback使用场景" aria-label="Permalink to &quot;真实的useCallback使用场景&quot;">​</a></h3><p>经过之前的说明，目前<code>useCallback</code>看起来并没有实际的用途，它没有减少函数的定义次数，甚至在不合理使用时还会出现闭包陷阱，而带来的唯一好处就是：保证函数指向确定且唯一</p><p>下面我们举一个实际场景来说明<code>useCallback</code>的用途：</p></div></div></main><footer class="VPDocFooter" data-v-25140dfd data-v-b9eb50cb><!--[--><!--]--><div class="edit-info" data-v-b9eb50cb><div class="edit-link" data-v-b9eb50cb><a class="VPLink link edit-link-button" href="https://github.com/ZiuChen/ZiuChen.github.io/edit/main/docs/note/React Hooks.md" target="_blank" rel="noreferrer" data-v-b9eb50cb data-v-fd6e3585><!--[--><svg xmlns="http://www.w3.org/2000/svg" viewbox="0 0 24 24" class="edit-link-icon" aria-label="edit icon" data-v-b9eb50cb><path d="M18,23H4c-1.7,0-3-1.3-3-3V6c0-1.7,1.3-3,3-3h7c0.6,0,1,0.4,1,1s-0.4,1-1,1H4C3.4,5,3,5.4,3,6v14c0,0.6,0.4,1,1,1h14c0.6,0,1-0.4,1-1v-7c0-0.6,0.4-1,1-1s1,0.4,1,1v7C21,21.7,19.7,23,18,23z"></path><path d="M8,17c-0.3,0-0.5-0.1-0.7-0.3C7,16.5,6.9,16.1,7,15.8l1-4c0-0.2,0.1-0.3,0.3-0.5l9.5-9.5c1.2-1.2,3.2-1.2,4.4,0c1.2,1.2,1.2,3.2,0,4.4l-9.5,9.5c-0.1,0.1-0.3,0.2-0.5,0.3l-4,1C8.2,17,8.1,17,8,17zM9.9,12.5l-0.5,2.1l2.1-0.5l9.3-9.3c0.4-0.4,0.4-1.1,0-1.6c-0.4-0.4-1.2-0.4-1.6,0l0,0L9.9,12.5z M18.5,2.5L18.5,2.5L18.5,2.5z"></path></svg> Edit this page on GitHub<!--]--><!----></a></div><div class="last-updated" data-v-b9eb50cb><p class="VPLastUpdated" data-v-b9eb50cb data-v-f683efee>Updated Date: <time datetime="2023-04-30T15:47:38.000Z" data-v-f683efee></time></p></div></div><div class="prev-next" data-v-b9eb50cb><div class="pager" data-v-b9eb50cb><a class="pager-link prev" href="/note/React.html" data-v-b9eb50cb><span class="desc" data-v-b9eb50cb>Previous page</span><span class="title" data-v-b9eb50cb>React基础</span></a></div><div class="has-prev pager" data-v-b9eb50cb><a class="pager-link next" href="/note/Redux.html" data-v-b9eb50cb><span class="desc" data-v-b9eb50cb>Next page</span><span class="title" data-v-b9eb50cb>Redux</span></a></div></div></footer><!--[--><!--]--></div></div></div><!--[--><!--]--></div></div><footer class="VPFooter has-sidebar" data-v-6305e88a data-v-58542612><div class="container" data-v-58542612><p class="message" data-v-58542612>Released under the MIT License.</p><p class="copyright" data-v-58542612>Copyright © 2019-present Ziu Chen</p></div></footer><!--[--><!--]--></div></div>
<script>__VP_HASH_MAP__ = JSON.parse("{\"article_【2023】青训营 - 前端练习题汇总解析.md\":\"6916c0ec\",\"article_【字节跳动】前端面试题总结.md\":\"701c53fb\",\"article_浅析defineproperty与proxy实现的双向绑定.md\":\"521252f4\",\"article_深入vue3源码，看看vue.use后究竟发生了什么？.md\":\"18476e6b\",\"article_深入理解proxy与reflect.md\":\"b45c59e4\",\"article_深入javascript数据类型.md\":\"0504df2d\",\"article_深入理解浏览器缓存机制.md\":\"39f550bf\",\"article_深入理解浏览器运行原理.md\":\"793514b2\",\"index.md\":\"9aea996d\",\"note_front-end engineering.md\":\"c2748bcf\",\"article_【快手】深入理解前端面试题.md\":\"1e8bbcca\",\"note_css.md\":\"13a2c74a\",\"article_【用友金融】前端面试题总结.md\":\"c4da9be4\",\"article_一文读懂事件冒泡与事件捕获.md\":\"968df563\",\"note_mysql.md\":\"7dd624f9\",\"article_一文读懂伪类与伪元素.md\":\"41bb4fdd\",\"note_react hooks.md\":\"1ee13841\",\"note_javascript.md\":\"f27de6d2\",\"article_一文读懂函数中this指向问题.md\":\"13544316\",\"article_从0实现一个年度报告.md\":\"4b88fa98\",\"article_彻底搞懂对象的数据属性描述符、存储属性描述符.md\":\"3d90f158\",\"note_react router.md\":\"c2ca63bf\",\"note_javascriptenhanced.md\":\"64b06c8e\",\"note_redux.md\":\"0644f046\",\"note_react.md\":\"5fccce47\",\"project_jsrunner_log_index.md\":\"b8214c06\",\"project_markdown_index.md\":\"e155b8c3\",\"project_markdown_log_index.md\":\"63f53fc4\",\"project_markdown_shortcut_index.md\":\"927480f8\",\"project_smartwordbreak_log_index.md\":\"69d30c27\",\"self_index.md\":\"0ab0eb59\",\"note_ssr.md\":\"0b644b9d\",\"works_opensource.md\":\"21573cff\",\"project_clipboardmanager_index.md\":\"ad0fc1e2\",\"project_clipboardmanager_log_index.md\":\"3650aaf8\",\"project_smartwordbreak_index.md\":\"67e233f2\",\"project_clipboardmanager_statement_index.md\":\"49d061fc\",\"project_clipboardmanager_vip_index.md\":\"093f61a7\",\"project_smartwordbreak_statement_index.md\":\"5bf1ac63\",\"project_jsrunner_index.md\":\"1f84fdde\",\"works_contribution.md\":\"a447f397\",\"project_clipboardmanager_guide_index.md\":\"d1a48958\"}")
__VP_SITE_DATA__ = JSON.parse("{\"lang\":\"en-US\",\"dir\":\"ltr\",\"title\":\"ZiuChen\",\"description\":\"Unlimited Progress.\",\"base\":\"/\",\"head\":[],\"appearance\":true,\"themeConfig\":{\"logo\":\"/logo.png\",\"nav\":[{\"text\":\"首页\",\"link\":\"/\"},{\"text\":\"我的项目\",\"items\":[{\"text\":\"超级剪贴板\",\"link\":\"/project/ClipboardManager/\"},{\"text\":\"超级Markdown\",\"link\":\"/project/Markdown/\"},{\"text\":\"超级JavaScript\",\"link\":\"/project/JSRunner/\"},{\"text\":\"超级分词\",\"link\":\"/project/SmartWordBreak/\"}]},{\"text\":\"开源作品\",\"items\":[{\"text\":\"个人作品\",\"link\":\"/works/opensource\"},{\"text\":\"社区贡献\",\"link\":\"/works/contribution\"}]},{\"text\":\"学习笔记\",\"items\":[{\"text\":\"JavaScript基础\",\"link\":\"/note/JavaScript\"},{\"text\":\"CSS基础\",\"link\":\"/note/CSS\"},{\"text\":\"JavaScript进阶\",\"link\":\"/note/JavaScriptEnhanced\"},{\"text\":\"前端工程化\",\"link\":\"/note/Front-end Engineering\"},{\"text\":\"服务端渲染\",\"link\":\"/note/SSR\"},{\"text\":\"React基础\",\"link\":\"/note/React\"},{\"text\":\"React Hooks\",\"link\":\"/note/React Hooks\"},{\"text\":\"Redux\",\"link\":\"/note/Redux\"},{\"text\":\"React Router\",\"link\":\"/note/React Router\"},{\"text\":\"MySQL\",\"link\":\"/note/MySQL\"}]},{\"text\":\"个人介绍\",\"link\":\"/self/\"}],\"sidebar\":[{\"text\":\"我的项目\",\"items\":[{\"text\":\"超级剪贴板\",\"link\":\"/project/ClipboardManager/\"},{\"text\":\"超级Markdown\",\"link\":\"/project/Markdown/\"},{\"text\":\"超级JavaScript\",\"link\":\"/project/JSRunner/\"},{\"text\":\"超级分词\",\"link\":\"/project/SmartWordBreak/\"}]},{\"text\":\"开源作品\",\"collapsed\":true,\"items\":[{\"text\":\"个人作品\",\"link\":\"/works/opensource\"},{\"text\":\"社区贡献\",\"link\":\"/works/contribution\"}]},{\"text\":\"文章归档\",\"collapsed\":true,\"items\":[{\"text\":\"【2023】青训营 - 前端练习题汇总解析\",\"link\":\"/article/【2023】青训营 - 前端练习题汇总解析\"},{\"text\":\"【字节跳动】前端面试题总结\",\"link\":\"/article/【字节跳动】前端面试题总结\"},{\"text\":\"【快手】深入理解前端面试题\",\"link\":\"/article/【快手】深入理解前端面试题\"},{\"text\":\"【用友金融】前端面试题总结\",\"link\":\"/article/【用友金融】前端面试题总结\"},{\"text\":\"一文读懂事件冒泡与事件捕获\",\"link\":\"/article/一文读懂事件冒泡与事件捕获\"},{\"text\":\"一文读懂伪类与伪元素\",\"link\":\"/article/一文读懂伪类与伪元素\"},{\"text\":\"一文读懂函数中this指向问题\",\"link\":\"/article/一文读懂函数中this指向问题\"},{\"text\":\"从0实现一个年度报告\",\"link\":\"/article/从0实现一个年度报告\"},{\"text\":\"彻底搞懂对象的数据属性描述符、存储属性描述符\",\"link\":\"/article/彻底搞懂对象的数据属性描述符、存储属性描述符\"},{\"text\":\"浅析defineProperty与Proxy实现的双向绑定\",\"link\":\"/article/浅析defineProperty与Proxy实现的双向绑定\"},{\"text\":\"深入JavaScript数据类型\",\"link\":\"/article/深入JavaScript数据类型\"},{\"text\":\"深入Vue3源码，看看Vue.use后究竟发生了什么？\",\"link\":\"/article/深入Vue3源码，看看Vue.use后究竟发生了什么？\"},{\"text\":\"深入理解Proxy与Reflect\",\"link\":\"/article/深入理解Proxy与Reflect\"},{\"text\":\"深入理解浏览器缓存机制\",\"link\":\"/article/深入理解浏览器缓存机制\"},{\"text\":\"深入理解浏览器运行原理\",\"link\":\"/article/深入理解浏览器运行原理\"}]},{\"text\":\"学习笔记\",\"collapsed\":true,\"items\":[{\"text\":\"JavaScript基础\",\"link\":\"/note/JavaScript\"},{\"text\":\"CSS基础\",\"link\":\"/note/CSS\"},{\"text\":\"JavaScript进阶\",\"link\":\"/note/JavaScriptEnhanced\"},{\"text\":\"前端工程化\",\"link\":\"/note/Front-end Engineering\"},{\"text\":\"服务端渲染\",\"link\":\"/note/SSR\"},{\"text\":\"React基础\",\"link\":\"/note/React\"},{\"text\":\"React Hooks\",\"link\":\"/note/React Hooks\"},{\"text\":\"Redux\",\"link\":\"/note/Redux\"},{\"text\":\"React Router\",\"link\":\"/note/React Router\"},{\"text\":\"MySQL\",\"link\":\"/note/MySQL\"}]}],\"socialLinks\":[{\"icon\":\"github\",\"link\":\"https://github.com/ZiuChen\"},{\"icon\":{\"svg\":\"<svg width=\\\"36\\\" height=\\\"28\\\" viewBox=\\\"0 0 36 28\\\" fill=\\\"none\\\" xmlns=\\\"http://www.w3.org/2000/svg\\\"><path fill-rule=\\\"evenodd\\\" clip-rule=\\\"evenodd\\\" d=\\\"M17.5875 6.77268L21.8232 3.40505L17.5875 0.00748237L17.5837 0L13.3555 3.39757L17.5837 6.76894L17.5875 6.77268ZM17.5863 17.3955H17.59L28.5161 8.77432L25.5526 6.39453L17.59 12.6808H17.5863L17.5825 12.6845L9.61993 6.40201L6.66016 8.78181L17.5825 17.3992L17.5863 17.3955ZM17.5828 23.2891L17.5865 23.2854L32.2133 11.7456L35.1768 14.1254L28.5238 19.3752L17.5865 28L0.284376 14.3574L0 14.1291L2.95977 11.7531L17.5828 23.2891Z\\\" fill=\\\"#1E80FF\\\"/></svg>\"},\"link\":\"https://juejin.cn/user/1887205216238477\"}],\"editLink\":{\"pattern\":\"https://github.com/ZiuChen/ZiuChen.github.io/edit/main/docs/:path\",\"text\":\"Edit this page on GitHub\"},\"footer\":{\"message\":\"Released under the MIT License.\",\"copyright\":\"Copyright © 2019-present Ziu Chen\"},\"lastUpdatedText\":\"Updated Date\",\"search\":{\"provider\":\"algolia\",\"options\":{\"appId\":\"LFZ2CPWWUG\",\"apiKey\":\"b4fd296ea5e467b3ac4a582160ff3122\",\"indexName\":\"ziuchenio\"}}},\"locales\":{},\"scrollOffset\":90,\"cleanUrls\":false}")</script>
</body>
</html>
Reference in New Issue View Git Blame Copy Permalink