mirror of
https://github.com/facebook/react-native.git
synced 2025-11-01 09:14:26 +00:00
Website Deployment Script
52 lines
30 KiB
HTML
52 lines
30 KiB
HTML
<!doctype html>
|
|
<html lang="en">
|
|
<head>
|
|
<meta charset="UTF-8">
|
|
<meta name="viewport" content="width=device-width,initial-scale=1">
|
|
<meta name="generator" content="Docusaurus v2.0.0-alpha.70">
|
|
<link rel="alternate" type="application/rss+xml" href="/blog/rss.xml" title="React Native Blog RSS Feed">
|
|
<link rel="alternate" type="application/atom+xml" href="/blog/atom.xml" title="React Native Blog Atom Feed">
|
|
<link rel="preconnect" href="https://www.google-analytics.com">
|
|
<script>window.ga=window.ga||function(){(ga.q=ga.q||[]).push(arguments)},ga.l=+new Date,ga("create","UA-41298772-2","auto"),ga("send","pageview")</script>
|
|
<script async src="https://www.google-analytics.com/analytics.js"></script>
|
|
<link rel="preconnect" href="https://www.google-analytics.com">
|
|
<link rel="preconnect" href="https://www.googletagmanager.com">
|
|
<script async src="https://www.googletagmanager.com/gtag/js?id=UA-41298772-2"></script>
|
|
<script>function gtag(){dataLayer.push(arguments)}window.dataLayer=window.dataLayer||[],gtag("js",new Date),gtag("config","UA-41298772-2",{})</script>
|
|
<link rel="search" type="application/opensearchdescription+xml" title="React Native" href="/opensearch.xml">
|
|
<link rel="icon" href="/img/pwa/manifest-icon-512.png">
|
|
<link rel="manifest" href="/manifest.json">
|
|
<meta name="theme-color" content="#20232a">
|
|
<meta name="apple-mobile-web-app-capable" content="yes">
|
|
<meta name="apple-mobile-web-app-status-bar-style" content="#20232a">
|
|
<link rel="apple-touch-icon" href="/img/pwa/manifest-icon-512.png">
|
|
<link rel="mask-icon" href="/img/pwa/manifest-icon-512.png" color="#06bcee">
|
|
<meta name="msapplication-TileImage" href="/img/pwa/manifest-icon-512.png">
|
|
<meta name="msapplication-TileColor" content="#20232a">
|
|
<script src="https://cdn.jsdelivr.net/npm/focus-visible@5.2.0/dist/focus-visible.min.js" defer="defer"></script>
|
|
<script src="https://snack.expo.io/embed.js" defer="defer"></script><title data-react-helmet="true">Fast Refresh · React Native</title><meta data-react-helmet="true" name="twitter:image:alt" content="Image for React Native"><meta data-react-helmet="true" name="docsearch:language" content="en"><meta data-react-helmet="true" name="docsearch:version" content="0.63"><meta data-react-helmet="true" name="docsearch:docusaurus_tag" content="docs-default-0.63"><meta data-react-helmet="true" property="og:image" content="https://reactnative.dev/img/logo-og.png"><meta data-react-helmet="true" name="twitter:card" content="summary"><meta data-react-helmet="true" name="twitter:image" content="https://reactnative.dev/img/logo-og.png"><meta data-react-helmet="true" property="og:title" content="Fast Refresh · React Native"><meta data-react-helmet="true" name="description" content="Fast Refresh is a React Native feature that allows you to get near-instant feedback for changes in your React components. Fast Refresh is enabled by default, and you can toggle "Enable Fast Refresh" in the React Native developer menu. With Fast Refresh enabled, most edits should be visible within a second or two."><meta data-react-helmet="true" property="og:description" content="Fast Refresh is a React Native feature that allows you to get near-instant feedback for changes in your React components. Fast Refresh is enabled by default, and you can toggle "Enable Fast Refresh" in the React Native developer menu. With Fast Refresh enabled, most edits should be visible within a second or two."><meta data-react-helmet="true" property="og:url" content="https://reactnative.dev/docs/fast-refresh"><link data-react-helmet="true" rel="shortcut icon" href="/img/favicon.ico"><link data-react-helmet="true" rel="preconnect" href="https://BH4D9OD16A-dsn.algolia.net" crossorigin="anonymous"><link data-react-helmet="true" rel="canonical" href="https://reactnative.dev/docs/fast-refresh"><link rel="stylesheet" href="/styles.f56da522.css">
|
|
<link rel="stylesheet" href="/main.3de2b5ef.css">
|
|
<link rel="preload" href="/styles.dfe3b9eb.js" as="script">
|
|
<link rel="preload" href="/runtime~main.5916a0a4.js" as="script">
|
|
<link rel="preload" href="/main.6094b97f.js" as="script">
|
|
<link rel="preload" href="/1.8c647f8e.js" as="script">
|
|
<link rel="preload" href="/2.e133592c.js" as="script">
|
|
<link rel="preload" href="/931.624ff15d.js" as="script">
|
|
<link rel="preload" href="/ee5b3385.2b5a4e6d.js" as="script">
|
|
<link rel="preload" href="/17896441.1e68c5df.js" as="script">
|
|
<link rel="preload" href="/9cdda500.774c4d81.js" as="script">
|
|
</head>
|
|
<body>
|
|
<script>!function(){function t(t){document.documentElement.setAttribute("data-theme",t)}var e=function(){var t=null;try{t=localStorage.getItem("theme")}catch(t){}return t}();t(null!==e?e:"light")}()</script><div id="__docusaurus">
|
|
<nav aria-label="Skip navigation links"><button type="button" tabindex="0" class="skipToContent_3aLp">Skip to main content</button></nav><nav class="navbar navbar--fixed-top navbar--dark"><div class="navbar__inner"><div class="navbar__items"><div aria-label="Navigation bar toggle" class="navbar__toggle" role="button" tabindex="0"><svg aria-label="Menu" width="30" height="30" viewBox="0 0 30 30" role="img" focusable="false"><title>Menu</title><path stroke="currentColor" stroke-linecap="round" stroke-miterlimit="10" stroke-width="2" d="M4 7h22M4 15h22M4 23h22"></path></svg></div><a class="navbar__brand" href="/"><img src="/img/header_logo.svg" alt="React Native" class="themedImage_phiS themedImage--light_VJaY navbar__logo"><img src="/img/header_logo.svg" alt="React Native" class="themedImage_phiS themedImage--dark_1NF3 navbar__logo"><strong class="navbar__title">React Native</strong></a><div class="navbar__item dropdown dropdown--hoverable dropdown--left"><a class="navbar__item navbar__link" href="/docs/getting-started">0.63</a><ul class="dropdown__menu"><li><a class="dropdown__link" href="/docs/next/fast-refresh">Next</a></li><li><a aria-current="page" class="dropdown__link dropdown__link--active" href="/docs/fast-refresh">0.63</a></li><li><a class="dropdown__link" href="/docs/0.62/fast-refresh">0.62</a></li><li><a class="dropdown__link" href="/docs/0.61/fast-refresh">0.61</a></li><li><a class="dropdown__link" href="/docs/0.60/fast-refresh">0.60</a></li><li><a class="dropdown__link" href="/versions">All versions</a></li></ul></div></div><div class="navbar__items navbar__items--right"><a class="navbar__item navbar__link navbar__link--active" href="/docs/getting-started">Docs</a><a class="navbar__item navbar__link" href="/docs/components-and-apis">Components</a><a class="navbar__item navbar__link" href="/docs/accessibilityinfo">API</a><a class="navbar__item navbar__link" href="/help">Community</a><a class="navbar__item navbar__link" href="/blog">Blog</a><a href="https://github.com/facebook/react-native" target="_blank" rel="noopener noreferrer" class="navbar__item navbar__link navbar-github-link" aria-label="GitHub repository"></a><div class="react-toggle react-toggle--disabled displayOnlyInLargeViewport_Bh6k"><div class="react-toggle-track"><div class="react-toggle-track-check"><span class="toggle_1UDy">🌜</span></div><div class="react-toggle-track-x"><span class="toggle_1UDy">🌞</span></div></div><div class="react-toggle-thumb"></div><input type="checkbox" disabled="" aria-label="Dark mode toggle" class="react-toggle-screenreader-only"></div><button type="button" class="DocSearch DocSearch-Button" aria-label="Search"><span class="DocSearch-Button-Container"><svg width="20" height="20" class="DocSearch-Search-Icon" viewBox="0 0 20 20"><path d="M14.386 14.386l4.0877 4.0877-4.0877-4.0877c-2.9418 2.9419-7.7115 2.9419-10.6533 0-2.9419-2.9418-2.9419-7.7115 0-10.6533 2.9418-2.9419 7.7115-2.9419 10.6533 0 2.9419 2.9418 2.9419 7.7115 0 10.6533z" stroke="currentColor" fill="none" fill-rule="evenodd" stroke-linecap="round" stroke-linejoin="round"></path></svg><span class="DocSearch-Button-Placeholder">Search</span></span></button></div></div><div role="presentation" class="navbar-sidebar__backdrop"></div><div class="navbar-sidebar"><div class="navbar-sidebar__brand"><a class="navbar__brand" href="/"><img src="/img/header_logo.svg" alt="React Native" class="themedImage_phiS themedImage--light_VJaY navbar__logo"><img src="/img/header_logo.svg" alt="React Native" class="themedImage_phiS themedImage--dark_1NF3 navbar__logo"><strong class="navbar__title">React Native</strong></a></div><div class="navbar-sidebar__items"><div class="menu"><ul class="menu__list"><li class="menu__list-item"><a class="menu__link navbar__link--active" href="/docs/getting-started">Docs</a></li><li class="menu__list-item"><a class="menu__link" href="/docs/components-and-apis">Components</a></li><li class="menu__list-item"><a class="menu__link" href="/docs/accessibilityinfo">API</a></li><li class="menu__list-item"><a class="menu__link" href="/help">Community</a></li><li class="menu__list-item"><a class="menu__link" href="/blog">Blog</a></li><li class="menu__list-item"><a role="button" class="menu__link menu__link--sublist">Versions</a><ul class="menu__list"><li class="menu__list-item"><a class="menu__link" href="/docs/next/fast-refresh">Next</a></li><li class="menu__list-item"><a aria-current="page" class="menu__link menu__link--active" href="/docs/fast-refresh">0.63</a></li><li class="menu__list-item"><a class="menu__link" href="/docs/0.62/fast-refresh">0.62</a></li><li class="menu__list-item"><a class="menu__link" href="/docs/0.61/fast-refresh">0.61</a></li><li class="menu__list-item"><a class="menu__link" href="/docs/0.60/fast-refresh">0.60</a></li><li class="menu__list-item"><a class="menu__link" href="/versions">All versions</a></li></ul></li><li class="menu__list-item"><a href="https://github.com/facebook/react-native" target="_blank" rel="noopener noreferrer" class="menu__link navbar-github-link" aria-label="GitHub repository"></a></li></ul></div></div></div></nav><div class="main-wrapper"><div class="docPage_1mVJ"><div class="docSidebarContainer_uPTz" role="complementary"><div class="sidebar_M-Lc"><div class="menu menu--responsive thin-scrollbar menu_tgpy"><button aria-label="Open Menu" aria-haspopup="true" class="button button--secondary button--sm menu__button" type="button"><svg aria-label="Menu" class="sidebarMenuIcon_1e05" width="24" height="24" viewBox="0 0 30 30" role="img" focusable="false"><title>Menu</title><path stroke="currentColor" stroke-linecap="round" stroke-miterlimit="10" stroke-width="2" d="M4 7h22M4 15h22M4 23h22"></path></svg></button><ul class="menu__list"><li class="menu__list-item menu__list-item--collapsed"><a class="menu__link menu__link--sublist" href="#!">The Basics</a><ul class="menu__list"><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/getting-started">Introduction</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/intro-react-native-components">Core Components and Native Components</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/intro-react">React Fundamentals</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/handling-text-input">Handling Text Input</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/using-a-scrollview">Using a ScrollView</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/using-a-listview">Using List Views</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/troubleshooting">Troubleshooting</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/platform-specific-code">Platform Specific Code</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/more-resources">More Resources</a></li></ul></li><li class="menu__list-item menu__list-item--collapsed"><a class="menu__link menu__link--sublist" href="#!">Environment setup</a><ul class="menu__list"><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/environment-setup">Setting up the development environment</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/integration-with-existing-apps">Integration with Existing Apps</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/building-for-tv">Building For TV Devices</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/out-of-tree-platforms">Out-of-Tree Platforms</a></li></ul></li><li class="menu__list-item"><a class="menu__link menu__link--sublist menu__link--active" href="#!">Workflow</a><ul class="menu__list"><li class="menu__list-item"><a class="menu__link" tabindex="0" href="/docs/running-on-device">Running On Device</a></li><li class="menu__list-item"><a aria-current="page" class="menu__link menu__link--active active" tabindex="0" href="/docs/fast-refresh">Fast Refresh</a></li><li class="menu__list-item"><a class="menu__link" tabindex="0" href="/docs/debugging">Debugging</a></li><li class="menu__list-item"><a class="menu__link" tabindex="0" href="/docs/testing-overview">Testing</a></li><li class="menu__list-item"><a class="menu__link" tabindex="0" href="/docs/libraries">Using Libraries</a></li><li class="menu__list-item"><a class="menu__link" tabindex="0" href="/docs/typescript">Using TypeScript</a></li><li class="menu__list-item"><a class="menu__link" tabindex="0" href="/docs/upgrading">Upgrading to new React Native versions</a></li></ul></li><li class="menu__list-item menu__list-item--collapsed"><a class="menu__link menu__link--sublist" href="#!">Design</a><ul class="menu__list"><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/style">Style</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/height-and-width">Height and Width</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/flexbox">Layout with Flexbox</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/images">Images</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/colors">Color Reference</a></li></ul></li><li class="menu__list-item menu__list-item--collapsed"><a class="menu__link menu__link--sublist" href="#!">Interaction</a><ul class="menu__list"><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/handling-touches">Handling Touches</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/navigation">Navigating Between Screens</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/animations">Animations</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/gesture-responder-system">Gesture Responder System</a></li></ul></li><li class="menu__list-item menu__list-item--collapsed"><a class="menu__link menu__link--sublist" href="#!">Inclusion</a><ul class="menu__list"><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/accessibility">Accessibility</a></li></ul></li><li class="menu__list-item menu__list-item--collapsed"><a class="menu__link menu__link--sublist" href="#!">Performance</a><ul class="menu__list"><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/performance">Performance Overview</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/optimizing-flatlist-configuration">Optimizing Flatlist Configuration</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/ram-bundles-inline-requires">RAM Bundles and Inline Requires</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/profiling">Profiling</a></li></ul></li><li class="menu__list-item menu__list-item--collapsed"><a class="menu__link menu__link--sublist" href="#!">JavaScript Runtime</a><ul class="menu__list"><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/javascript-environment">JavaScript Environment</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/timers">Timers</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/hermes">Using Hermes</a></li></ul></li><li class="menu__list-item menu__list-item--collapsed"><a class="menu__link menu__link--sublist" href="#!">Connectivity</a><ul class="menu__list"><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/network">Networking</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/security">Security</a></li></ul></li><li class="menu__list-item menu__list-item--collapsed"><a class="menu__link menu__link--sublist" href="#!">Native Modules</a><ul class="menu__list"><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/native-modules-intro">Native Modules Intro</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/native-modules-android">Android Native Modules</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/native-modules-ios">iOS Native Modules</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/native-modules-setup">Native Modules NPM Package Setup</a></li></ul></li><li class="menu__list-item menu__list-item--collapsed"><a class="menu__link menu__link--sublist" href="#!">Native Components</a><ul class="menu__list"><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/native-components-android">Android Native UI Components</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/native-components-ios">iOS Native UI Components</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/direct-manipulation">Direct Manipulation</a></li></ul></li><li class="menu__list-item menu__list-item--collapsed"><a class="menu__link menu__link--sublist" href="#!">Guides (Android)</a><ul class="menu__list"><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/headless-js-android">Headless JS</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/signed-apk-android">Publishing to Google Play Store</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/removing-default-permissions">Removing Default Permissions</a></li></ul></li><li class="menu__list-item menu__list-item--collapsed"><a class="menu__link menu__link--sublist" href="#!">Guides (iOS)</a><ul class="menu__list"><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/linking-libraries-ios">Linking Libraries</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/running-on-simulator-ios">Running On Simulator</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/communication-ios">Communication between native and React Native</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/app-extensions">App Extensions</a></li></ul></li></ul></div></div></div><main class="docMainContainer_1zi2"><div class="container padding-vert--lg docItemWrapper_1hMI"><div class="row"><div class="col docItemCol_2AGf"><div class="docItemContainer_1tAC"><article><header><h1 class="docTitle_cWlf">Fast Refresh</h1></header><div class="markdown"><p>Fast Refresh is a React Native feature that allows you to get near-instant feedback for changes in your React components. Fast Refresh is enabled by default, and you can toggle "Enable Fast Refresh" in the React Native developer menu. With Fast Refresh enabled, most edits should be visible within a second or two.</p><h2><a aria-hidden="true" tabindex="-1" class="anchor enhancedAnchor_E4oP" id="how-it-works"></a>How It Works<a class="hash-link" href="#how-it-works" title="Direct link to heading">#</a></h2><ul><li>If you edit a module that <strong>only exports React component(s)</strong>, Fast Refresh will update the code only for that module, and re-render your component. You can edit anything in that file, including styles, rendering logic, event handlers, or effects.</li><li>If you edit a module with exports that <em>aren't</em> React components, Fast Refresh will re-run both that module, and the other modules importing it. So if both <code>Button.js</code> and <code>Modal.js</code> import <code>Theme.js</code>, editing <code>Theme.js</code> will update both components.</li><li>Finally, if you <strong>edit a file</strong> that's <strong>imported by modules outside of the React tree</strong>, Fast Refresh <strong>will fall back to doing a full reload</strong>. You might have a file which renders a React component but also exports a value that is imported by a <strong>non-React component</strong>. For example, maybe your component also exports a constant, and a non-React utility module imports it. In that case, consider migrating the query to a separate file and importing it into both files. This will re-enable Fast Refresh to work. Other cases can usually be solved in a similar way.</li></ul><h2><a aria-hidden="true" tabindex="-1" class="anchor enhancedAnchor_E4oP" id="error-resilience"></a>Error Resilience<a class="hash-link" href="#error-resilience" title="Direct link to heading">#</a></h2><p>If you make a <strong>syntax error</strong> during a Fast Refresh session, you can fix it and save the file again. The redbox will disappear. Modules with syntax errors are prevented from running, so you won't need to reload the app.</p><p>If you make a <strong>runtime error during the module initialization</strong> (for example, typing <code>Style.create</code> instead of <code>StyleSheet.create</code>), the Fast Refresh session will continue once you fix the error. The redbox will disappear, and the module will be updated.</p><p>If you make a mistake that leads to a <strong>runtime error inside your component</strong>, the Fast Refresh session will <em>also</em> continue after you fix the error. In that case, React will remount your application using the updated code.</p><p>If you have <a href="https://reactjs.org/docs/error-boundaries.html" target="_blank" rel="noopener noreferrer">error boundaries</a> in your app (which is a good idea for graceful failures in production), they will retry rendering on the next edit after a redbox. In that sense, having an error boundary can prevent you from always getting kicked out to the root app screen. However, keep in mind that error boundaries shouldn't be <em>too</em> granular. They are used by React in production, and should always be designed intentionally.</p><h2><a aria-hidden="true" tabindex="-1" class="anchor enhancedAnchor_E4oP" id="limitations"></a>Limitations<a class="hash-link" href="#limitations" title="Direct link to heading">#</a></h2><p>Fast Refresh tries to preserve local React state in the component you're editing, but only if it's safe to do so. Here's a few reasons why you might see local state being reset on every edit to a file:</p><ul><li>Local state is not preserved for class components (only function components and Hooks preserve state).</li><li>The module you're editing might have <em>other</em> exports in addition to a React component.</li><li>Sometimes, a module would export the result of calling higher-order component like <code>createNavigationContainer(MyScreen)</code>. If the returned component is a class, state will be reset.</li></ul><p>In the longer term, as more of your codebase moves to function components and Hooks, you can expect state to be preserved in more cases.</p><h2><a aria-hidden="true" tabindex="-1" class="anchor enhancedAnchor_E4oP" id="tips"></a>Tips<a class="hash-link" href="#tips" title="Direct link to heading">#</a></h2><ul><li>Fast Refresh preserves React local state in function components (and Hooks) by default.</li><li>Sometimes you might want to <em>force</em> the state to be reset, and a component to be remounted. For example, this can be handy if you're tweaking an animation that only happens on mount. To do this, you can add <code>// @refresh reset</code> anywhere in the file you're editing. This directive is local to the file, and instructs Fast Refresh to remount components defined in that file on every edit.</li></ul><h2><a aria-hidden="true" tabindex="-1" class="anchor enhancedAnchor_E4oP" id="fast-refresh-and-hooks"></a>Fast Refresh and Hooks<a class="hash-link" href="#fast-refresh-and-hooks" title="Direct link to heading">#</a></h2><p>When possible, Fast Refresh attempts to preserve the state of your component between edits. In particular, <code>useState</code> and <code>useRef</code> preserve their previous values as long as you don't change their arguments or the order of the Hook calls.</p><p>Hooks with dependencies—such as <code>useEffect</code>, <code>useMemo</code>, and <code>useCallback</code>—will <em>always</em> update during Fast Refresh. Their list of dependencies will be ignored while Fast Refresh is happening.</p><p>For example, when you edit <code>useMemo(() => x * 2, [x])</code> to <code>useMemo(() => x * 10, [x])</code>, it will re-run even though <code>x</code> (the dependency) has not changed. If React didn't do that, your edit wouldn't reflect on the screen!</p><p>Sometimes, this can lead to unexpected results. For example, even a <code>useEffect</code> with an empty array of dependencies would still re-run once during Fast Refresh. However, writing code resilient to an occasional re-running of <code>useEffect</code> is a good practice even without Fast Refresh. This makes it easier for you to later introduce new dependencies to it.</p></div></article><div class="docMetadata margin-vert--xl"><div class="row"><div class="col"><a href="https://github.com/facebook/react-native-website/blob/master/website/versioned_docs/version-0.63/fast-refresh.md" target="_blank" rel="noreferrer noopener"><svg fill="currentColor" height="1.2em" width="1.2em" preserveAspectRatio="xMidYMid meet" role="img" viewBox="0 0 40 40" class="iconEdit_2Hwv"><g><path d="m34.5 11.7l-3 3.1-6.3-6.3 3.1-3q0.5-0.5 1.2-0.5t1.1 0.5l3.9 3.9q0.5 0.4 0.5 1.1t-0.5 1.2z m-29.5 17.1l18.4-18.5 6.3 6.3-18.4 18.4h-6.3v-6.2z"></path></g></svg>Edit this page</a></div><div class="col text--right"><em><small class="docMetadata-updated">Last updated on <time datetime="2020-10-29T04:19:29.000Z" class="docLastUpdatedAt_1gIo">10/29/2020</time></small></em></div></div></div><div class="margin-vert--lg"><nav class="pagination-nav" aria-label="Blog list page navigation"><div class="pagination-nav__item"><a class="pagination-nav__link" href="/docs/running-on-device"><div class="pagination-nav__sublabel">Previous</div><div class="pagination-nav__label">« Running On Device</div></a></div><div class="pagination-nav__item pagination-nav__item--next"><a class="pagination-nav__link" href="/docs/debugging"><div class="pagination-nav__sublabel">Next</div><div class="pagination-nav__label">Debugging »</div></a></div></nav></div></div></div><div class="col col--3"><div class="tableOfContents_1zTD thin-scrollbar"><ul class="table-of-contents table-of-contents__left-border"><li><a href="#how-it-works" class="table-of-contents__link">How It Works</a></li><li><a href="#error-resilience" class="table-of-contents__link">Error Resilience</a></li><li><a href="#limitations" class="table-of-contents__link">Limitations</a></li><li><a href="#tips" class="table-of-contents__link">Tips</a></li><li><a href="#fast-refresh-and-hooks" class="table-of-contents__link">Fast Refresh and Hooks</a></li></ul></div></div></div></div></main></div></div><footer class="footer footer--dark"><div class="container"><div class="row footer__links"><div class="col footer__col"><h4 class="footer__title">Docs</h4><ul class="footer__items"><li class="footer__item"><a class="footer__link-item" href="/docs/getting-started">Getting Started</a></li><li class="footer__item"><a class="footer__link-item" href="/docs/tutorial">Tutorial</a></li><li class="footer__item"><a class="footer__link-item" href="/docs/components-and-apis">Components and APIs</a></li><li class="footer__item"><a class="footer__link-item" href="/docs/more-resources">More Resources</a></li></ul></div><div class="col footer__col"><h4 class="footer__title">Community</h4><ul class="footer__items"><li class="footer__item"><a class="footer__link-item" href="/help">The React Native Community</a></li><li class="footer__item"><a class="footer__link-item" href="/showcase">Who's using React Native?</a></li><li class="footer__item"><a href="https://stackoverflow.com/questions/tagged/react-native" target="_blank" rel="noopener noreferrer" class="footer__link-item">Ask Questions on Stack Overflow</a></li><li class="footer__item"><a href="https://github.com/facebook/react-native/blob/master/CONTRIBUTING.md" target="_blank" rel="noopener noreferrer" class="footer__link-item">Contributor Guide</a></li><li class="footer__item"><a href="https://dev.to/t/reactnative" target="_blank" rel="noopener noreferrer" class="footer__link-item">DEV Community</a></li></ul></div><div class="col footer__col"><h4 class="footer__title">Find us</h4><ul class="footer__items"><li class="footer__item"><a class="footer__link-item" href="/blog">Blog</a></li><li class="footer__item"><a href="https://twitter.com/reactnative" target="_blank" rel="noopener noreferrer" class="footer__link-item">Twitter</a></li><li class="footer__item"><a href="https://github.com/facebook/react-native" target="_blank" rel="noopener noreferrer" class="footer__link-item">GitHub</a></li></ul></div><div class="col footer__col"><h4 class="footer__title">More</h4><ul class="footer__items"><li class="footer__item"><a href="https://reactjs.org/" target="_blank" rel="noopener noreferrer" class="footer__link-item">React</a></li><li class="footer__item"><a href="https://opensource.facebook.com/legal/privacy" target="_blank" rel="noopener noreferrer" class="footer__link-item">Privacy Policy</a></li><li class="footer__item"><a href="https://opensource.facebook.com/legal/terms" target="_blank" rel="noopener noreferrer" class="footer__link-item">Terms of Service</a></li></ul></div></div><div class="footer__bottom text--center"><div class="margin-bottom--sm"><a href="https://opensource.facebook.com" target="_blank" rel="noopener noreferrer" class="footerLogoLink_3cAK"><img class="footer__logo" alt="Facebook Open Source Logo" src="/img/oss_logo.png"></a></div><div class="footer__copyright">Copyright © 2021 Facebook, Inc.</div></div></div></footer></div>
|
|
<script src="/styles.dfe3b9eb.js"></script>
|
|
<script src="/runtime~main.5916a0a4.js"></script>
|
|
<script src="/main.6094b97f.js"></script>
|
|
<script src="/1.8c647f8e.js"></script>
|
|
<script src="/2.e133592c.js"></script>
|
|
<script src="/931.624ff15d.js"></script>
|
|
<script src="/ee5b3385.2b5a4e6d.js"></script>
|
|
<script src="/17896441.1e68c5df.js"></script>
|
|
<script src="/9cdda500.774c4d81.js"></script>
|
|
</body>
|
|
</html> |