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<!DOCTYPE html><html><head><meta charset="utf-8"><meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1"><title>Timers – React Native | A framework for building native apps using React</title><meta name="viewport" content="width=device-width"><meta property="og:title" content="Timers – React Native | A framework for building native apps using React"><meta property="og:type" content="website"><meta property="og:url" content="http://facebook.github.io/react-native/index.html"><meta property="og:image" content="http://facebook.github.io/react-native/img/opengraph.png?2"><meta property="og:description" content="A framework for building native apps using React"><link rel="shortcut icon" href="/react-native/img/favicon.png?2"><link rel="stylesheet" href="/react-native/css/react-native.css"><script type="text/javascript" src="//use.typekit.net/vqa1hcx.js"></script><script type="text/javascript">try{Typekit.load();}catch(e){}</script></head><body><div class="container"><div class="nav-main"><div class="wrap"><a class="nav-home" href="/react-native/"><img src="/react-native/img/header_logo.png">React Native</a><div class="nav-site-wrapper"><ul class="nav-site nav-site-internal"><li><a href="/react-native/docs/getting-started.html" class="active">Docs</a></li><li><a href="/react-native/support.html" class="">Support</a></li><li><a href="https://github.com/facebook/react-native/releases" class="">Releases</a></li><li><a href="http://reactnative.cc" class="">Newsletter</a></li><li><a href="/react-native/showcase.html" class="">Showcase</a></li></ul><ul class="nav-site nav-site-external"><li><a href="https://github.com/facebook/react-native" class="">GitHub</a></li><li><a href="http://facebook.github.io/react" class="">React</a></li></ul></div></div></div><section class="content wrap documentationContent"><div class="nav-docs"><div class="nav-docs-section"><h3>Quick Start</h3><ul><li><a style="margin-left:0;" class="" href="/react-native/docs/getting-started.html#content">Getting Started</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/android-setup.html#content">Android Setup</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/tutorial.html#content">Tutorial</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/videos.html#content">Videos</a></li></ul></div><div class="nav-docs-section"><h3>Guides</h3><ul><li><a style="margin-left:0;" class="" href="/react-native/docs/style.html#content">Style</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/gesture-responder-system.html#content">Gesture Responder System</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/animations.html#content">Animations</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/accessibility.html#content">Accessibility</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/direct-manipulation.html#content">Direct Manipulation</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/debugging.html#content">Debugging</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/testing.html#content">Testing</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/javascript-environment.html#content">JavaScript Environment</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/navigator-comparison.html#content">Navigator Comparison</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/known-issues.html#content">Known Issues</a></li></ul></div><div class="nav-docs-section"><h3>Guides (iOS)</h3><ul><li><a style="margin-left:0;" class="" href="/react-native/docs/native-modules-ios.html#content">Native Modules</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/native-components-ios.html#content">Native UI Components</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/linking-libraries-ios.html#content">Linking Libraries</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/running-on-device-ios.html#content">Running On Device</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/embedded-app-ios.html#content">Integrating with Existing Apps</a></li></ul></div><div class="nav-docs-section"><h3>Guides (Android)</h3><ul><li><a style="margin-left:0;" class="" href="/react-native/docs/native-modules-android.html#content">Native Modules</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/native-components-android.html#content">Native UI Components</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/running-on-device-android.html#content">Running On Device</a></li></ul></div><div class="nav-docs-section"><h3>components</h3><ul><li><a style="margin-left:0;" class="" href="/react-native/docs/activityindicatorios.html#content">ActivityIndicatorIOS</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/datepickerios.html#content">DatePickerIOS</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/drawerlayoutandroid.html#content">DrawerLayoutAndroid</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/image.html#content">Image</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/listview.html#content">ListView</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/mapview.html#content">MapView</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/navigator.html#content">Navigator</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/modal.html#content">Modal</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/navigatorios.html#content">NavigatorIOS</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/pickerios.html#content">PickerIOS</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/progressbarandroid.html#content">ProgressBarAndroid</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/progressviewios.html#content">ProgressViewIOS</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/scrollview.html#content">ScrollView</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/segmentedcontrolios.html#content">SegmentedControlIOS</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/sliderios.html#content">SliderIOS</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/switchandroid.html#content">SwitchAndroid</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/switchios.html#content">SwitchIOS</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/tabbarios.html#content">TabBarIOS</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/tabbarios-item.html#content">TabBarIOS.Item</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/text.html#content">Text</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/textinput.html#content">TextInput</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/toolbarandroid.html#content">ToolbarAndroid</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/touchablehighlight.html#content">TouchableHighlight</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/touchablenativefeedback.html#content">TouchableNativeFeedback</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/touchableopacity.html#content">TouchableOpacity</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/touchablewithoutfeedback.html#content">TouchableWithoutFeedback</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/view.html#content">View</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/webview.html#content">WebView</a></li></ul></div><div class="nav-docs-section"><h3>apis</h3><ul><li><a style="margin-left:0;" class="" href="/react-native/docs/actionsheetios.html#content">ActionSheetIOS</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/alertios.html#content">AlertIOS</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/animated.html#content">Animated</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/appregistry.html#content">AppRegistry</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/appstateios.html#content">AppStateIOS</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/asyncstorage.html#content">AsyncStorage</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/backandroid.html#content">BackAndroid</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/cameraroll.html#content">CameraRoll</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/interactionmanager.html#content">InteractionManager</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/layoutanimation.html#content">LayoutAnimation</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/linkingios.html#content">LinkingIOS</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/netinfo.html#content">NetInfo</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/panresponder.html#content">PanResponder</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/pixelratio.html#content">PixelRatio</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/pushnotificationios.html#content">PushNotificationIOS</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/statusbarios.html#content">StatusBarIOS</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/stylesheet.html#content">StyleSheet</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/toastandroid.html#content">ToastAndroid</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/vibrationios.html#content">VibrationIOS</a></li></ul></div><div class="nav-docs-section"><h3>Polyfills</h3><ul><li><a style="margin-left:0;" class="" href="/react-native/docs/flexbox.html#content">Flexbox</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/geolocation.html#content">Geolocation</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/network.html#content">Network</a></li><li><a style="margin-left:0;" class="active" href="/react-native/docs/timers.html#content">Timers</a></li></ul></div></div><div class="inner-content"><a id="content"></a><h1>Timers</h1><div><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" target="_blank">browser timers</a>.</p><h2><a class="anchor" name="timers"></a>Timers <a class="hash-link" href="#timers">#</a></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" name="interactionmanager"></a>InteractionManager <a class="hash-link" href="#interactionmanager">#</a></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><div class="prism language-javascript">InteractionManager<span class="token punctuation">.</span><span class="token function">runAfterInteractions<span class="token punctuation">(</span></span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">=</span><span class="token operator">></span> <span class="token punctuation">{</span>
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<span class="token comment" spellcheck="true"> // ...long-running synchronous task...
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</span><span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span></div><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><div class="prism language-javascript"><span class="token keyword">var</span> handle <span class="token operator">=</span> InteractionManager<span class="token punctuation">.</span><span class="token function">createInteractionHandle<span class="token punctuation">(</span></span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token comment" spellcheck="true">
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// run animation... (`runAfterInteractions` tasks are queued)
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</span><span class="token comment" spellcheck="true">// later, on animation completion:
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</span>InteractionManager<span class="token punctuation">.</span><span class="token function">clearInteractionHandle<span class="token punctuation">(</span></span>handle<span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token comment" spellcheck="true">
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// queued tasks run if all handles were cleared</span></div><h2><a class="anchor" name="timermixin"></a>TimerMixin <a class="hash-link" href="#timermixin">#</a></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><div class="prism language-javascript"><span class="token keyword">var</span> TimerMixin <span class="token operator">=</span> <span class="token function">require<span class="token punctuation">(</span></span><span class="token string">'react-timer-mixin'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
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<span class="token keyword">var</span> Component <span class="token operator">=</span> React<span class="token punctuation">.</span><span class="token function">createClass<span class="token punctuation">(</span></span><span class="token punctuation">{</span>
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mixins<span class="token punctuation">:</span> <span class="token punctuation">[</span>TimerMixin<span class="token punctuation">]</span><span class="token punctuation">,</span>
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componentDidMount<span class="token punctuation">:</span> <span class="token keyword">function</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
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<span class="token keyword">this</span><span class="token punctuation">.</span><span class="token function">setTimeout<span class="token punctuation">(</span></span>
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<span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">=</span><span class="token operator">></span> <span class="token punctuation">{</span> console<span class="token punctuation">.</span><span class="token function">log<span class="token punctuation">(</span></span><span class="token string">'I do not leak!'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token punctuation">}</span><span class="token punctuation">,</span>
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<span class="token number">500</span>
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<span class="token punctuation">)</span><span class="token punctuation">;</span>
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<span class="token punctuation">}</span>
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<span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span></div><p>We strongly discourage using the global <code>setTimeout(...)</code> and recommend instead that you use <code>this.setTimeout(...)</code> provided by react-timer-mixin. 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></div><div class="docs-prevnext"></div></div></section><footer class="wrap"><div class="right">© 2015 Facebook Inc.</div></footer></div><div id="fb-root"></div><script>
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