mirror of
https://github.com/facebook/react.git
synced 2025-11-01 09:12:30 +00:00
Paul O’Shannessy
59fe162fe5
Commits synced:009be62906af79caf1aa5167b7a5b2f728846712af7ea7c999287db7017e14580fb012f27175d166663dd6f5b3df72bd76be05cc7b635cfbbace6b696323db7c18cdac160439dea228e4aeb360ed80dd67c68612c0c4ed2c1c90
477 lines
19 KiB
HTML
477 lines
19 KiB
HTML
<!DOCTYPE html>
|
|
<!--[if IE]><![endif]-->
|
|
<html>
|
|
<head>
|
|
<meta charset="utf-8">
|
|
<meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">
|
|
<title>React | Immutability Helpers</title>
|
|
<meta name="viewport" content="width=device-width">
|
|
<meta property="og:title" content="React | Immutability Helpers" />
|
|
<meta property="og:type" content="website" />
|
|
<meta property="og:url" content="http://facebook.github.io/react/docs/update.html" />
|
|
<meta property="og:image" content="http://facebook.github.io/react/img/logo_og.png" />
|
|
<meta property="og:description" content="A JavaScript library for building user interfaces" />
|
|
<meta property="fb:app_id" content="623268441017527" />
|
|
|
|
<link rel="shortcut icon" href="/react/favicon.ico">
|
|
<link rel="alternate" type="application/rss+xml" title="React" href="http://facebook.github.io/react/feed.xml">
|
|
|
|
<link rel="stylesheet" href="/react/css/syntax.css">
|
|
<link rel="stylesheet" href="/react/css/codemirror.css">
|
|
<link rel="stylesheet" href="/react/css/react.css">
|
|
|
|
<script type="text/javascript" src="//use.typekit.net/vqa1hcx.js"></script>
|
|
<script type="text/javascript">try{Typekit.load();}catch(e){}</script>
|
|
|
|
<!--[if lte IE 8]>
|
|
<script type="text/javascript" src="/react/js/html5shiv.min.js"></script>
|
|
<script type="text/javascript" src="/react/js/es5-shim.min.js"></script>
|
|
<script type="text/javascript" src="/react/js/es5-sham.min.js"></script>
|
|
<![endif]-->
|
|
<script type="text/javascript" src="/react/js/codemirror.js"></script>
|
|
<script type="text/javascript" src="/react/js/javascript.js"></script>
|
|
<script type="text/javascript" src="/react/js/react.js"></script>
|
|
<script type="text/javascript" src="/react/js/JSXTransformer.js"></script>
|
|
<script type="text/javascript" src="/react/js/live_editor.js"></script>
|
|
<script type="text/javascript" src="/react/js/showdown.js"></script>
|
|
</head>
|
|
<body>
|
|
|
|
<div class="container">
|
|
|
|
<div class="nav-main">
|
|
<div class="wrap">
|
|
<a class="nav-home" href="/react/index.html">
|
|
<img class="nav-logo" alt="" src="/react/img/logo_small.png" width="38" height="38">
|
|
React
|
|
</a>
|
|
<ul class="nav-site">
|
|
<li><a href="/react/docs/getting-started.html" class="active">docs</a></li>
|
|
<li><a href="/react/support.html">support</a></li>
|
|
<li><a href="/react/downloads.html">download</a></li>
|
|
<li><a href="/react/blog/">blog</a></li>
|
|
<li><a href="http://github.com/facebook/react">github</a>
|
|
</ul>
|
|
</div>
|
|
</div>
|
|
|
|
|
|
|
|
<section class="content wrap documentationContent">
|
|
<div class="nav-docs">
|
|
<!-- Docs Nav -->
|
|
|
|
<div class="nav-docs-section">
|
|
<h3>Quick Start</h3>
|
|
<ul>
|
|
|
|
<li>
|
|
<a href="/react/docs/getting-started.html">
|
|
Getting Started
|
|
</a>
|
|
|
|
</li>
|
|
|
|
<li>
|
|
<a href="/react/docs/tutorial.html">
|
|
Tutorial
|
|
</a>
|
|
|
|
</li>
|
|
|
|
<li>
|
|
<a href="/react/docs/thinking-in-react.html">
|
|
Thinking in React
|
|
</a>
|
|
|
|
</li>
|
|
|
|
</ul>
|
|
</div>
|
|
|
|
<div class="nav-docs-section">
|
|
<h3>Community Resources</h3>
|
|
<ul>
|
|
|
|
<li>
|
|
<a href="/react/docs/videos.html">
|
|
Videos
|
|
</a>
|
|
|
|
</li>
|
|
|
|
<li>
|
|
<a href="/react/docs/complementary-tools.html">
|
|
Complementary Tools
|
|
</a>
|
|
|
|
</li>
|
|
|
|
<li>
|
|
<a href="/react/docs/examples.html">
|
|
Examples
|
|
</a>
|
|
|
|
</li>
|
|
|
|
</ul>
|
|
</div>
|
|
|
|
<div class="nav-docs-section">
|
|
<h3>Guides</h3>
|
|
<ul>
|
|
|
|
<li>
|
|
<a href="/react/docs/why-react.html">
|
|
Why React?
|
|
</a>
|
|
|
|
</li>
|
|
|
|
<li>
|
|
<a href="/react/docs/displaying-data.html">
|
|
Displaying Data
|
|
</a>
|
|
|
|
<ul>
|
|
|
|
<li>
|
|
<a href="/react/docs/jsx-in-depth.html">
|
|
JSX in Depth
|
|
</a>
|
|
</li>
|
|
|
|
<li>
|
|
<a href="/react/docs/jsx-gotchas.html">
|
|
JSX Gotchas
|
|
</a>
|
|
</li>
|
|
|
|
</ul>
|
|
|
|
</li>
|
|
|
|
<li>
|
|
<a href="/react/docs/interactivity-and-dynamic-uis.html">
|
|
Interactivity and Dynamic UIs
|
|
</a>
|
|
|
|
</li>
|
|
|
|
<li>
|
|
<a href="/react/docs/multiple-components.html">
|
|
Multiple Components
|
|
</a>
|
|
|
|
</li>
|
|
|
|
<li>
|
|
<a href="/react/docs/reusable-components.html">
|
|
Reusable Components
|
|
</a>
|
|
|
|
</li>
|
|
|
|
<li>
|
|
<a href="/react/docs/forms.html">
|
|
Forms
|
|
</a>
|
|
|
|
</li>
|
|
|
|
<li>
|
|
<a href="/react/docs/working-with-the-browser.html">
|
|
Working With the Browser
|
|
</a>
|
|
|
|
<ul>
|
|
|
|
<li>
|
|
<a href="/react/docs/more-about-refs.html">
|
|
More About Refs
|
|
</a>
|
|
</li>
|
|
|
|
</ul>
|
|
|
|
</li>
|
|
|
|
<li>
|
|
<a href="/react/docs/tooling-integration.html">
|
|
Tooling Integration
|
|
</a>
|
|
|
|
</li>
|
|
|
|
<li>
|
|
<a href="/react/docs/addons.html">
|
|
Add-Ons
|
|
</a>
|
|
|
|
<ul>
|
|
|
|
<li>
|
|
<a href="/react/docs/animation.html">
|
|
Animation
|
|
</a>
|
|
</li>
|
|
|
|
<li>
|
|
<a href="/react/docs/two-way-binding-helpers.html">
|
|
Two-Way Binding Helpers
|
|
</a>
|
|
</li>
|
|
|
|
<li>
|
|
<a href="/react/docs/class-name-manipulation.html">
|
|
Class Name Manipulation
|
|
</a>
|
|
</li>
|
|
|
|
<li>
|
|
<a href="/react/docs/test-utils.html">
|
|
Test Utilities
|
|
</a>
|
|
</li>
|
|
|
|
<li>
|
|
<a href="/react/docs/clone-with-props.html">
|
|
Cloning Components
|
|
</a>
|
|
</li>
|
|
|
|
<li>
|
|
<a href="/react/docs/update.html" class="active">
|
|
Immutability Helpers
|
|
</a>
|
|
</li>
|
|
|
|
</ul>
|
|
|
|
</li>
|
|
|
|
</ul>
|
|
</div>
|
|
|
|
<div class="nav-docs-section">
|
|
<h3>Reference</h3>
|
|
<ul>
|
|
|
|
<li>
|
|
<a href="/react/docs/top-level-api.html">
|
|
Top-Level API
|
|
</a>
|
|
|
|
</li>
|
|
|
|
<li>
|
|
<a href="/react/docs/component-api.html">
|
|
Component API
|
|
</a>
|
|
|
|
</li>
|
|
|
|
<li>
|
|
<a href="/react/docs/component-specs.html">
|
|
Component Specs and Lifecycle
|
|
</a>
|
|
|
|
</li>
|
|
|
|
<li>
|
|
<a href="/react/docs/tags-and-attributes.html">
|
|
Supported Tags and Attributes
|
|
</a>
|
|
|
|
</li>
|
|
|
|
<li>
|
|
<a href="/react/docs/events.html">
|
|
Event System
|
|
</a>
|
|
|
|
</li>
|
|
|
|
<li>
|
|
<a href="/react/docs/dom-differences.html">
|
|
DOM Differences
|
|
</a>
|
|
|
|
</li>
|
|
|
|
<li>
|
|
<a href="/react/docs/special-non-dom-attributes.html">
|
|
Special Non-DOM Attributes
|
|
</a>
|
|
|
|
</li>
|
|
|
|
<li>
|
|
<a href="/react/docs/reconciliation.html">
|
|
Reconciliation
|
|
</a>
|
|
|
|
</li>
|
|
|
|
</ul>
|
|
</div>
|
|
|
|
|
|
<!-- Tips Nav -->
|
|
|
|
<div class="nav-docs-section">
|
|
<h3>Tips</h3>
|
|
<ul>
|
|
|
|
<li>
|
|
<a href="/react/tips/introduction.html">Introduction</a>
|
|
</li>
|
|
|
|
<li>
|
|
<a href="/react/tips/inline-styles.html">Inline Styles</a>
|
|
</li>
|
|
|
|
<li>
|
|
<a href="/react/tips/if-else-in-JSX.html">If-Else in JSX</a>
|
|
</li>
|
|
|
|
<li>
|
|
<a href="/react/tips/self-closing-tag.html">Self-Closing Tag</a>
|
|
</li>
|
|
|
|
<li>
|
|
<a href="/react/tips/maximum-number-of-jsx-root-nodes.html">Maximum Number of JSX Root Nodes</a>
|
|
</li>
|
|
|
|
<li>
|
|
<a href="/react/tips/style-props-value-px.html">Shorthand for Specifying Pixel Values in style props</a>
|
|
</li>
|
|
|
|
<li>
|
|
<a href="/react/tips/children-props-type.html">Type of the Children props</a>
|
|
</li>
|
|
|
|
<li>
|
|
<a href="/react/tips/controlled-input-null-value.html">Value of null for Controlled Input</a>
|
|
</li>
|
|
|
|
<li>
|
|
<a href="/react/tips/componentWillReceiveProps-not-triggered-after-mounting.html">componentWillReceiveProps Not Triggered After Mounting</a>
|
|
</li>
|
|
|
|
<li>
|
|
<a href="/react/tips/props-in-getInitialState-as-anti-pattern.html">Props in getInitialState Is an Anti-Pattern</a>
|
|
</li>
|
|
|
|
<li>
|
|
<a href="/react/tips/dom-event-listeners.html">DOM Event Listeners in a Component</a>
|
|
</li>
|
|
|
|
<li>
|
|
<a href="/react/tips/initial-ajax.html">Load Initial Data via AJAX</a>
|
|
</li>
|
|
|
|
<li>
|
|
<a href="/react/tips/false-in-jsx.html">False in JSX</a>
|
|
</li>
|
|
|
|
<li>
|
|
<a href="/react/tips/communicate-between-components.html">Communicate Between Components</a>
|
|
</li>
|
|
|
|
<li>
|
|
<a href="/react/tips/expose-component-functions.html">Expose Component Functions</a>
|
|
</li>
|
|
|
|
</ul>
|
|
</div>
|
|
|
|
</div>
|
|
|
|
|
|
<div class="inner-content">
|
|
<h1>Immutability Helpers</h1>
|
|
<div class="subHeader"></div>
|
|
<p>React lets you use whatever style of data management you want, including mutation. However, if you can use immutable data in performance-critical parts of your application it's easy to implement a fast <code>shouldComponentUpdate()</code> method to significantly speed up your app.</p>
|
|
|
|
<p>Dealing with immutable data in JavaScript is more difficult than in languages designed for it, like <a href="http://clojure.org/">Clojure</a>. However, we've provided a simple immutability helper, <code>update()</code>, that makes dealing with this type of data much easier, <em>without</em> fundamentally changing how your data is represented.</p>
|
|
<h2><a class="anchor" name="the-main-idea"></a>The main idea <a class="hash-link" href="#the-main-idea">#</a></h2>
|
|
<p>If you mutate data like this:</p>
|
|
<div class="highlight"><pre><code class="javascript language-javascript" data-lang="javascript"><span class="nx">myData</span><span class="p">.</span><span class="nx">x</span><span class="p">.</span><span class="nx">y</span><span class="p">.</span><span class="nx">z</span> <span class="o">=</span> <span class="mi">7</span><span class="p">;</span>
|
|
<span class="nx">myData</span><span class="p">.</span><span class="nx">a</span><span class="p">.</span><span class="nx">b</span><span class="p">.</span><span class="nx">push</span><span class="p">(</span><span class="mi">9</span><span class="p">);</span>
|
|
</code></pre></div>
|
|
<p>you have no way of determining which data has changed since the previous copy is destroyed. Instead, you need to create a new copy of <code>myData</code> and change only the parts of it that need to be changed. Then you can compare the old copy of <code>myData</code> with the new one in <code>shouldComponentUpdate()</code> using triple-equals:</p>
|
|
<div class="highlight"><pre><code class="javascript language-javascript" data-lang="javascript"><span class="kd">var</span> <span class="nx">newData</span> <span class="o">=</span> <span class="nx">deepCopy</span><span class="p">(</span><span class="nx">myData</span><span class="p">);</span>
|
|
<span class="nx">newData</span><span class="p">.</span><span class="nx">x</span><span class="p">.</span><span class="nx">y</span><span class="p">.</span><span class="nx">z</span> <span class="o">=</span> <span class="mi">7</span><span class="p">;</span>
|
|
<span class="nx">newData</span><span class="p">.</span><span class="nx">a</span><span class="p">.</span><span class="nx">b</span><span class="p">.</span><span class="nx">push</span><span class="p">(</span><span class="mi">9</span><span class="p">);</span>
|
|
</code></pre></div>
|
|
<p>Unfortunately, deep copies are expensive, and sometimes impossible. You can alleviate this by only copying objects that need to be changed and by reusing the objects that haven't changed. Unfortunately, in today's JavaScript this can be cumbersome:</p>
|
|
<div class="highlight"><pre><code class="javascript language-javascript" data-lang="javascript"><span class="kd">var</span> <span class="nx">newData</span> <span class="o">=</span> <span class="nx">extend</span><span class="p">(</span><span class="nx">myData</span><span class="p">,</span> <span class="p">{</span>
|
|
<span class="nx">x</span><span class="o">:</span> <span class="nx">extend</span><span class="p">(</span><span class="nx">myData</span><span class="p">.</span><span class="nx">x</span><span class="p">,</span> <span class="p">{</span>
|
|
<span class="nx">y</span><span class="o">:</span> <span class="nx">extend</span><span class="p">(</span><span class="nx">myData</span><span class="p">.</span><span class="nx">x</span><span class="p">.</span><span class="nx">y</span><span class="p">,</span> <span class="p">{</span><span class="nx">z</span><span class="o">:</span> <span class="mi">7</span><span class="p">}),</span>
|
|
<span class="p">}),</span>
|
|
<span class="nx">a</span><span class="o">:</span> <span class="nx">extend</span><span class="p">(</span><span class="nx">myData</span><span class="p">.</span><span class="nx">a</span><span class="p">,</span> <span class="p">{</span><span class="nx">b</span><span class="o">:</span> <span class="nx">myData</span><span class="p">.</span><span class="nx">a</span><span class="p">.</span><span class="nx">b</span><span class="p">.</span><span class="nx">concat</span><span class="p">(</span><span class="mi">9</span><span class="p">)})</span>
|
|
<span class="p">});</span>
|
|
</code></pre></div>
|
|
<p>While this is fairly performant (since it only shallow copies <code>log n</code> objects and reuses the rest), it's a big pain to write. Look at all the repetition! This is not only annoying, but also provides a large surface area for bugs.</p>
|
|
|
|
<p><code>update()</code> provides simple syntactic sugar around this pattern to make writing this code easier. This code becomes:</p>
|
|
<div class="highlight"><pre><code class="javascript language-javascript" data-lang="javascript"><span class="kd">var</span> <span class="nx">newData</span> <span class="o">=</span> <span class="nx">React</span><span class="p">.</span><span class="nx">addons</span><span class="p">.</span><span class="nx">update</span><span class="p">(</span><span class="nx">myData</span><span class="p">,</span> <span class="p">{</span>
|
|
<span class="nx">x</span><span class="o">:</span> <span class="p">{</span><span class="nx">y</span><span class="o">:</span> <span class="p">{</span><span class="nx">z</span><span class="o">:</span> <span class="p">{</span><span class="nx">$set</span><span class="o">:</span> <span class="mi">7</span><span class="p">}}},</span>
|
|
<span class="nx">a</span><span class="o">:</span> <span class="p">{</span><span class="nx">b</span><span class="o">:</span> <span class="p">{</span><span class="nx">$push</span><span class="o">:</span> <span class="p">[</span><span class="mi">7</span><span class="p">]}}</span>
|
|
<span class="p">});</span>
|
|
</code></pre></div>
|
|
<p>While the syntax takes a little getting used to (though it's inspired by <a href="http://docs.mongodb.org/manual/core/crud-introduction/#query">MongoDB's query language</a>) there's no redundancy, it's statically analyzable and it's not much more typing than the mutative version.</p>
|
|
|
|
<p>The <code>$</code>-prefixed keys are called <em>directives</em>. The data structure they are "mutating" is called the <em>target</em>.</p>
|
|
<h2><a class="anchor" name="available-directives"></a>Available directives <a class="hash-link" href="#available-directives">#</a></h2>
|
|
<ul>
|
|
<li><code>{$push: array}</code> <code>push()</code> all the items in <code>array</code> on the target</li>
|
|
<li><code>{$unshift: array}</code> <code>unshift()</code> all the items in <code>array</code> on the target</li>
|
|
<li><code>{$splice: array of arrays}</code> for each item in <code>array()</code> call <code>splice()</code> on the target with the parameters provided by the item.</li>
|
|
<li><code>{$set: any}</code> replace the target entirely</li>
|
|
<li><code>{$merge: object}</code> merge the keys of <code>object</code> with the target</li>
|
|
</ul>
|
|
|
|
|
|
<div class="docs-prevnext">
|
|
|
|
<a class="docs-prev" href="/react/docs/clone-with-props.html">← Prev</a>
|
|
|
|
|
|
</div>
|
|
</div>
|
|
</section>
|
|
|
|
|
|
<footer class="wrap">
|
|
<div class="left">
|
|
A Facebook & Instagram collaboration.<br>
|
|
<a href="/react/acknowledgements.html">Acknowledgements</a>
|
|
</div>
|
|
<div class="right">© 2014 Facebook Inc.</div>
|
|
</footer>
|
|
</div>
|
|
<div id="fb-root"></div>
|
|
|
|
<script>
|
|
(function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){
|
|
(i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o),
|
|
m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m)
|
|
})(window,document,'script','//www.google-analytics.com/analytics.js','ga');
|
|
ga('create', 'UA-41298772-1', 'facebook.github.io');
|
|
ga('send', 'pageview');
|
|
|
|
!function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="https://platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs");
|
|
|
|
(function(d, s, id) {
|
|
var js, fjs = d.getElementsByTagName(s)[0];
|
|
if (d.getElementById(id)) return;
|
|
js = d.createElement(s); js.id = id;
|
|
js.src = "//connect.facebook.net/en_US/all.js#xfbml=1&appId=623268441017527";
|
|
fjs.parentNode.insertBefore(js, fjs);
|
|
}(document, 'script', 'facebook-jssdk'));
|
|
</script>
|
|
</body>
|
|
</html>
|