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<!DOCTYPE html><html lang="en"><head><meta charSet="utf-8"/><meta http-equiv="X-UA-Compatible" content="IE=edge"/><title>Timers · React Native</title><meta name="viewport" content="width=device-width"/><meta name="generator" content="Docusaurus"/><meta name="description" content="Timers are an important part of an application and React Native implements the [browser timers](https://developer.mozilla.org/en-US/Add-ons/Code_snippets/Timers)."/><meta name="docsearch:version" content="0.56"/><meta name="docsearch:language" content="en"/><meta property="og:title" content="Timers · React Native"/><meta property="og:type" content="website"/><meta property="og:url" content="https://facebook.github.io/react-native/index.html"/><meta property="og:description" content="Timers are an important part of an application and React Native implements the [browser timers](https://developer.mozilla.org/en-US/Add-ons/Code_snippets/Timers)."/><meta name="twitter:card" content="summary"/><link rel="shortcut icon" href="/react-native/img/favicon.png"/><link rel="stylesheet" href="https://cdn.jsdelivr.net/docsearch.js/1/docsearch.min.css"/><link rel="stylesheet" href="//cdnjs.cloudflare.com/ajax/libs/highlight.js/9.12.0/styles/solarized-dark.min.css"/><link rel="alternate" type="application/atom+xml" href="https://facebook.github.io/react-native/blog/atom.xml" title="React Native Blog ATOM Feed"/><link rel="alternate" type="application/rss+xml" href="https://facebook.github.io/react-native/blog/feed.xml" title="React Native Blog RSS Feed"/><script>
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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/react-native-website/blob/master/docs/timers.md" target="_blank" rel="noreferrer noopener">Edit</a><h1 class="postHeaderTitle">Timers</h1></header><article><div><span><p>Timers are an important part of an application and React Native implements the <a href="https://developer.mozilla.org/en-US/Add-ons/Code_snippets/Timers">browser timers</a>.</p>
<h2><a class="anchor" aria-hidden="true" id="timers"></a><a href="#timers" 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>Timers</h2>
<ul>
<li>setTimeout, clearTimeout</li>
<li>setInterval, clearInterval</li>
<li>setImmediate, clearImmediate</li>
<li>requestAnimationFrame, cancelAnimationFrame</li>
</ul>
<p><code>requestAnimationFrame(fn)</code> is not the same as <code>setTimeout(fn, 0)</code> - the former will fire after all the frame has flushed, whereas the latter will fire as quickly as possible (over 1000x per second on a iPhone 5S).</p>
<p><code>setImmediate</code> is executed at the end of the current JavaScript execution block, right before sending the batched response back to native. Note that if you call <code>setImmediate</code> within a <code>setImmediate</code> callback, it will be executed right away, it won't yield back to native in between.</p>
<p>The <code>Promise</code> implementation uses <code>setImmediate</code> as its asynchronicity primitive.</p>
<h2><a class="anchor" aria-hidden="true" id="interactionmanager"></a><a href="#interactionmanager" 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>InteractionManager</h2>
<p>One reason why well-built native apps feel so smooth is by avoiding expensive operations during interactions and animations. In React Native, we currently have a limitation that there is only a single JS execution thread, but you can use <code>InteractionManager</code> to make sure long-running work is scheduled to start after any interactions/animations have completed.</p>
<p>Applications can schedule tasks to run after interactions with the following:</p>
<pre><code class="hljs css languages- javascript">InteractionManager.runAfterInteractions(<span class="hljs-function"><span class="hljs-params">()</span> =&gt;</span> {
<span class="hljs-comment">// ...long-running synchronous task...</span>
});
</code></pre>
<p>Compare this to other scheduling alternatives:</p>
<ul>
<li>requestAnimationFrame(): for code that animates a view over time.</li>
<li>setImmediate/setTimeout/setInterval(): run code later, note this may delay animations.</li>
<li>runAfterInteractions(): run code later, without delaying active animations.</li>
</ul>
<p>The touch handling system considers one or more active touches to be an 'interaction' and will delay <code>runAfterInteractions()</code> callbacks until all touches have ended or been cancelled.</p>
<p>InteractionManager also allows applications to register animations by creating an interaction 'handle' on animation start, and clearing it upon completion:</p>
<pre><code class="hljs css languages- javascript"><span class="hljs-keyword">var</span> handle = InteractionManager.createInteractionHandle();
<span class="hljs-comment">// run animation... (`runAfterInteractions` tasks are queued)</span>
<span class="hljs-comment">// later, on animation completion:</span>
InteractionManager.clearInteractionHandle(handle);
<span class="hljs-comment">// queued tasks run if all handles were cleared</span>
</code></pre>
<h2><a class="anchor" aria-hidden="true" id="timermixin"></a><a href="#timermixin" 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>TimerMixin</h2>
<p>We found out that the primary cause of fatals in apps created with React Native was due to timers firing after a component was unmounted. To solve this recurring issue, we introduced <code>TimerMixin</code>. If you include <code>TimerMixin</code>, then you can replace your calls to <code>setTimeout(fn, 500)</code> with <code>this.setTimeout(fn, 500)</code> (just prepend <code>this.</code>) and everything will be properly cleaned up for you when the component unmounts.</p>
<p>This library does not ship with React Native - in order to use it on your project, you will need to install it with <code>npm i react-timer-mixin --save</code> from your project directory.</p>
<pre><code class="hljs css languages- javascript"><span class="hljs-keyword">import</span> TimerMixin <span class="hljs-keyword">from</span> <span class="hljs-string">'react-timer-mixin'</span>;
<span class="hljs-keyword">var</span> Component = createReactClass({
<span class="hljs-attr">mixins</span>: [TimerMixin],
<span class="hljs-attr">componentDidMount</span>: <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params"></span>) </span>{
<span class="hljs-keyword">this</span>.setTimeout(<span class="hljs-function"><span class="hljs-params">()</span> =&gt;</span> {
<span class="hljs-built_in">console</span>.log(<span class="hljs-string">'I do not leak!'</span>);
}, <span class="hljs-number">500</span>);
},
});
</code></pre>
<p>This will eliminate a lot of hard work tracking down bugs, such as crashes caused by timeouts firing after a component has been unmounted.</p>
<p>Keep in mind that if you use ES6 classes for your React components <a href="https://facebook.github.io/react/blog/2015/01/27/react-v0.13.0-beta-1.html#mixins">there is no built-in API for mixins</a>. To use <code>TimerMixin</code> with ES6 classes, we recommend <a href="https://github.com/brigand/react-mixin">react-mixin</a>.</p>
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