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<!DOCTYPE html><html lang="en"><head><meta charSet="utf-8"/><meta http-equiv="X-UA-Compatible" content="IE=edge"/><title>Code Splitting · Create React App</title><meta name="viewport" content="width=device-width"/><meta name="generator" content="Docusaurus"/><meta name="description" content="<p>Instead of downloading the entire app before users can use it, code splitting allows you to split your code into small chunks which you can then load on demand.</p>
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</script></nav></div><div class="container mainContainer"><div class="wrapper"><div class="post"><header class="postHeader"><a class="edit-page-link button" href="https://github.com/facebook/create-react-app/edit/master/docusaurus/docs/code-splitting.md" target="_blank" rel="noreferrer noopener">Edit</a><h1 class="postHeaderTitle">Code Splitting</h1></header><article><div><span><p>Instead of downloading the entire app before users can use it, code splitting allows you to split your code into small chunks which you can then load on demand.</p>
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<p>This project setup supports code splitting via <a href="http://2ality.com/2017/01/import-operator.html#loading-code-on-demand">dynamic <code>import()</code></a>. Its <a href="https://github.com/tc39/proposal-dynamic-import">proposal</a> is in stage 4. The <code>import()</code> function-like form takes the module name as an argument and returns a <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise"><code>Promise</code></a> which always resolves to the namespace object of the module.</p>
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<p>Here is an example:</p>
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<h2><a class="anchor" aria-hidden="true" id="moduleajs"></a><a href="#moduleajs" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a><code>moduleA.js</code></h2>
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<pre><code class="hljs css language-js"><span class="hljs-keyword">const</span> moduleA = <span class="hljs-string">'Hello'</span>;
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<span class="hljs-keyword">export</span> { moduleA };
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</code></pre>
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<h2><a class="anchor" aria-hidden="true" id="appjs"></a><a href="#appjs" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a><code>App.js</code></h2>
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<pre><code class="hljs css language-js"><span class="hljs-keyword">import</span> React, { Component } <span class="hljs-keyword">from</span> <span class="hljs-string">'react'</span>;
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<span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">App</span> <span class="hljs-keyword">extends</span> <span class="hljs-title">Component</span> </span>{
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handleClick = <span class="hljs-function"><span class="hljs-params">()</span> =></span> {
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<span class="hljs-keyword">import</span>(<span class="hljs-string">'./moduleA'</span>)
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.then(<span class="hljs-function">(<span class="hljs-params">{ moduleA }</span>) =></span> {
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<span class="hljs-comment">// Use moduleA</span>
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})
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.catch(<span class="hljs-function"><span class="hljs-params">err</span> =></span> {
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<span class="hljs-comment">// Handle failure</span>
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});
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};
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render() {
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<span class="hljs-keyword">return</span> (
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<span class="xml"><span class="hljs-tag"><<span class="hljs-name">div</span>></span>
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<span class="hljs-tag"><<span class="hljs-name">button</span> <span class="hljs-attr">onClick</span>=<span class="hljs-string">{this.handleClick}</span>></span>Load<span class="hljs-tag"></<span class="hljs-name">button</span>></span>
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<span class="hljs-tag"></<span class="hljs-name">div</span>></span></span>
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);
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}
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}
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<span class="hljs-keyword">export</span> <span class="hljs-keyword">default</span> App;
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</code></pre>
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<p>This will make <code>moduleA.js</code> and all its unique dependencies as a separate chunk that only loads after the user clicks the 'Load' button. For more information on the chunks that are created, see the <a href="/docs/production-build">production build</a> section.</p>
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<p>You can also use it with <code>async</code> / <code>await</code> syntax if you prefer it.</p>
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<h2><a class="anchor" aria-hidden="true" id="with-react-router"></a><a href="#with-react-router" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>With React Router</h2>
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<p>If you are using React Router check out <a href="https://serverless-stack.com/chapters/code-splitting-in-create-react-app.html">this tutorial</a> on how to use code splitting with it. You can find the companion GitHub repository <a href="https://github.com/AnomalyInnovations/serverless-stack-demo-client/tree/code-splitting-in-create-react-app">here</a>.</p>
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<p>Also check out the <a href="https://reactjs.org/docs/code-splitting.html">Code Splitting</a> section in React documentation.</p>
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</span></div></article></div><div class="docLastUpdate"><em>Last updated on 7/18/2019 by Ivan Pegashev</em></div><div class="docs-prevnext"><a class="docs-prev button" href="/docs/using-the-public-folder"><span class="arrow-prev">← </span><span>Using the Public Folder</span></a><a class="docs-next button" href="/docs/installing-a-dependency"><span>Installing a Dependency</span><span class="arrow-next"> →</span></a></div></div></div><nav class="onPageNav"><ul class="toc-headings"><li><a href="#moduleajs"><code>moduleA.js</code></a></li><li><a href="#appjs"><code>App.js</code></a></li><li><a href="#with-react-router">With React Router</a></li></ul></nav></div><footer class="nav-footer" id="footer"><section class="sitemap"><a href="/" class="nav-home"><img src="/img/logo.svg" alt="Create React App" width="66" height="58"/></a><div><h5>Docs</h5><a href="/docs/getting-started">Get Started</a><a href="https://reactjs.org/" target="_blank" rel="noreferrer noopener">Learn React</a></div><div><h5>Community</h5><a href="https://stackoverflow.com/questions/tagged/create-react-app" target="_blank" rel="noreferrer noopener">Stack Overflow</a><a href="https://spectrum.chat/create-react-app" target="_blank" rel="noreferrer noopener">Spectrum</a><a href="https://twitter.com/reactjs" target="_blank" rel="noreferrer noopener">Twitter</a></div><div><h5>More</h5><a href="https://www.github.com/facebook/create-react-app">GitHub</a><a class="github-button" href="https://github.com/facebook/create-react-app" data-icon="octicon-star" data-count-href="/facebook/create-react-app/stargazers" data-show-count="true" data-count-aria-label="# stargazers on GitHub" aria-label="Star this project on GitHub">Star</a></div></section><a href="https://code.facebook.com/projects/" target="_blank" rel="noreferrer noopener" class="fbOpenSource"><img src="/img/oss_logo.png" alt="Facebook Open Source" width="170" height="45"/></a><section class="copyright">Copyright © 2019 Facebook Inc.</section></footer></div><script type="text/javascript" src="https://cdn.jsdelivr.net/docsearch.js/1/docsearch.min.js"></script><script>
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