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"></path><polygon fill="currentColor" points=" 45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8, 14.9 62.8,22.9 71.5,22.9 "></polygon></svg></a></div></div></div></header><div class="css-xbsqlp css-15lkjjo"><div class="css-1m1176 css-95xunl"><div class="css-12vsfho"><div class="css-tctv7l"><div class="css-10335ra"><article class="css-174qq1k"><header class="css-hgc6lu"><h1 class="css-1obw60b">Error Boundaries</h1></header><div class="css-124oy3v"><div class="css-6nf64v"><div class="scary"> <blockquote> <p>These docs are old and won’t be updated. Go to <a href="https://react.dev/" target="_blank" rel="nofollow noopener noreferrer">react.dev</a> for the new React docs.</p> <p>These new documentation pages teach modern React:</p> <ul> <li><a href="https://react.dev/reference/react/Component#catching-rendering-errors-with-an-error-boundary" target="_blank" rel="nofollow noopener noreferrer"><code class="gatsby-code-text">React.Component</code>: Catching rendering errors with an error boundary</a></li> </ul> </blockquote> </div> <p>In the past, JavaScript errors inside components used to corrupt React’s internal state and cause it to <a href="https://github.com/facebook/react/issues/4026" target="_blank" rel="nofollow noopener noreferrer">emit</a> <a href="https://github.com/facebook/react/issues/6895" target="_blank" rel="nofollow noopener noreferrer">cryptic</a> <a href="https://github.com/facebook/react/issues/8579" target="_blank" rel="nofollow noopener noreferrer">errors</a> on next renders. These errors were always caused by an earlier error in the application code, but React did not provide a way to handle them gracefully in components, and could not recover from them.</p> <h2 id="introducing-error-boundaries"><a href="#introducing-error-boundaries" aria-hidden class="anchor"><svg 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>Introducing Error Boundaries </h2> <p>A JavaScript error in a part of the UI shouldn’t break the whole app. To solve this problem for React users, React 16 introduces a new concept of an “error boundary”.</p> <p>Error boundaries are React components that <strong>catch JavaScript errors anywhere in their child component tree, log those errors, and display a fallback UI</strong> instead of the component tree that crashed. Error boundaries catch errors during rendering, in lifecycle methods, and in constructors of the whole tree below them.</p> <blockquote> <p>Note</p> <p>Error boundaries do <strong>not</strong> catch errors for:</p> <ul> <li>Event handlers (<a href="#how-about-event-handlers">learn more</a>)</li> <li>Asynchronous code (e.g. <code class="gatsby-code-text">setTimeout</code> or <code class="gatsby-code-text">requestAnimationFrame</code> callbacks)</li> <li>Server side rendering</li> <li>Errors thrown in the error boundary itself (rather than its children)</li> </ul> </blockquote> <p>A class component becomes an error boundary if it defines either (or both) of the lifecycle methods <a href="/docs/react-component.html#static-getderivedstatefromerror"><code class="gatsby-code-text">static getDerivedStateFromError()</code></a> or <a href="/docs/react-component.html#componentdidcatch"><code class="gatsby-code-text">componentDidCatch()</code></a>. Use <code class="gatsby-code-text">static getDerivedStateFromError()</code> to render a fallback UI after an error has been thrown. Use <code class="gatsby-code-text">componentDidCatch()</code> to log error information.</p> <div class="gatsby-highlight has-highlighted-lines" data-language="jsx"><pre class="gatsby-code-jsx"><code class="gatsby-code-jsx"><span class="token keyword">class</span> <span class="token class-name">ErrorBoundary</span> <span class="token keyword">extends</span> <span class="token class-name">React<span class="token punctuation">.</span>Component</span> <span class="token punctuation">{</span> <span class="token function">constructor</span><span class="token punctuation">(</span><span class="token parameter">props</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token keyword">super</span><span class="token punctuation">(</span>props<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token keyword">this</span><span class="token punctuation">.</span>state <span class="token operator">=</span> <span class="token punctuation">{</span> <span class="token literal-property property">hasError</span><span class="token operator">:</span> <span class="token boolean">false</span> <span class="token punctuation">}</span><span class="token punctuation">;</span> <span class="token punctuation">}</span> <span class="gatsby-highlight-code-line"> <span class="token keyword">static</span> <span class="token function">getDerivedStateFromError</span><span class="token punctuation">(</span><span class="token parameter">error</span><span class="token punctuation">)</span> <span class="token punctuation">{</span></span><span class="gatsby-highlight-code-line"> <span class="token comment">// Update state so the next render will show the fallback UI.</span></span><span class="gatsby-highlight-code-line"> <span class="token keyword">return</span> <span class="token punctuation">{</span> <span class="token literal-property property">hasError</span><span class="token operator">:</span> <span class="token boolean">true</span> <span class="token punctuation">}</span><span class="token punctuation">;</span></span><span class="gatsby-highlight-code-line"> <span class="token punctuation">}</span></span> <span class="gatsby-highlight-code-line"> <span class="token function">componentDidCatch</span><span class="token punctuation">(</span><span class="token parameter">error<span class="token punctuation">,</span> errorInfo</span><span class="token punctuation">)</span> <span class="token punctuation">{</span></span><span class="gatsby-highlight-code-line"> <span class="token comment">// You can also log the error to an error reporting service</span></span><span class="gatsby-highlight-code-line"> <span class="token function">logErrorToMyService</span><span class="token punctuation">(</span>error<span class="token punctuation">,</span> errorInfo<span class="token punctuation">)</span><span class="token punctuation">;</span></span><span class="gatsby-highlight-code-line"> <span class="token punctuation">}</span></span> <span class="token function">render</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="gatsby-highlight-code-line"> <span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token keyword">this</span><span class="token punctuation">.</span>state<span class="token punctuation">.</span>hasError<span class="token punctuation">)</span> <span class="token punctuation">{</span></span><span class="gatsby-highlight-code-line"> <span class="token comment">// You can render any custom fallback UI</span></span><span class="gatsby-highlight-code-line"> <span class="token keyword">return</span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>h1</span><span class="token punctuation">></span></span><span class="token plain-text">Something went wrong.</span><span class="token tag"><span class="token tag"><span class="token punctuation"></</span>h1</span><span class="token punctuation">></span></span><span class="token punctuation">;</span></span><span class="gatsby-highlight-code-line"> <span class="token punctuation">}</span></span> <span class="token keyword">return</span> <span class="token keyword">this</span><span class="token punctuation">.</span>props<span class="token punctuation">.</span>children<span class="token punctuation">;</span> <span class="token punctuation">}</span> <span class="token punctuation">}</span></code></pre></div> <p>Then you can use it as a regular component:</p> <div class="gatsby-highlight" data-language="jsx"><pre class="gatsby-code-jsx"><code class="gatsby-code-jsx"><span class="token tag"><span class="token tag"><span class="token punctuation"><</span><span class="token class-name">ErrorBoundary</span></span><span class="token punctuation">></span></span><span class="token plain-text"> </span><span class="token tag"><span class="token tag"><span class="token punctuation"><</span><span class="token class-name">MyWidget</span></span> <span class="token punctuation">/></span></span><span class="token plain-text"> </span><span class="token tag"><span class="token tag"><span class="token punctuation"></</span><span class="token class-name">ErrorBoundary</span></span><span class="token punctuation">></span></span></code></pre></div> <p>Error boundaries work like a JavaScript <code class="gatsby-code-text">catch {}</code> block, but for components. Only class components can be error boundaries. In practice, most of the time you’ll want to declare an error boundary component once and use it throughout your application.</p> <p>Note that <strong>error boundaries only catch errors in the components below them in the tree</strong>. An error boundary can’t catch an error within itself. If an error boundary fails trying to render the error message, the error will propagate to the closest error boundary above it. This, too, is similar to how the <code class="gatsby-code-text">catch {}</code> block works in JavaScript.</p> <h2 id="live-demo"><a href="#live-demo" aria-hidden class="anchor"><svg 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>Live Demo </h2> <p>Check out <a href="https://codepen.io/gaearon/pen/wqvxGa?editors=0010" target="_blank" rel="nofollow noopener noreferrer">this example of declaring and using an error boundary</a>.</p> <h2 id="where-to-place-error-boundaries"><a href="#where-to-place-error-boundaries" aria-hidden class="anchor"><svg 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>Where to Place Error Boundaries </h2> <p>The granularity of error boundaries is up to you. You may wrap top-level route components to display a “Something went wrong” message to the user, just like how server-side frameworks often handle crashes. You may also wrap individual widgets in an error boundary to protect them from crashing the rest of the application.</p> <h2 id="new-behavior-for-uncaught-errors"><a href="#new-behavior-for-uncaught-errors" aria-hidden class="anchor"><svg 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>New Behavior for Uncaught Errors </h2> <p>This change has an important implication. <strong>As of React 16, errors that were not caught by any error boundary will result in unmounting of the whole React component tree.</strong></p> <p>We debated this decision, but in our experience it is worse to leave corrupted UI in place than to completely remove it. For example, in a product like Messenger leaving the broken UI visible could lead to somebody sending a message to the wrong person. Similarly, it is worse for a payments app to display a wrong amount than to render nothing.</p> <p>This change means that as you migrate to React 16, you will likely uncover existing crashes in your application that have been unnoticed before. Adding error boundaries lets you provide better user experience when something goes wrong.</p> <p>For example, Facebook Messenger wraps content of the sidebar, the info panel, the conversation log, and the message input into separate error boundaries. If some component in one of these UI areas crashes, the rest of them remain interactive.</p> <p>We also encourage you to use JS error reporting services (or build your own) so that you can learn about unhandled exceptions as they happen in production, and fix them.</p> <h2 id="component-stack-traces"><a href="#component-stack-traces" aria-hidden class="anchor"><svg 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>Component Stack Traces </h2> <p>React 16 prints all errors that occurred during rendering to the console in development, even if the application accidentally swallows them. In addition to the error message and the JavaScript stack, it also provides component stack traces. Now you can see where exactly in the component tree the failure has happened:</p> <a class="gatsby-resp-image-link" href="/static/f1276837b03821b43358d44c14072945/c3a47/error-boundaries-stack-trace.png" style="display: block" target="_blank" rel="noopener"> <span class="gatsby-resp-image-wrapper" style="position: relative; display: block; max-width: 840px; margin-left: auto; margin-right: auto;"> <span class="gatsby-resp-image-background-image" style="padding-bottom: 17.142857142857142%; position: relative; bottom: 0; left: 0; background-image: url('data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABQAAAADCAIAAAAcOLh5AAAACXBIWXMAABYlAAAWJQFJUiTwAAAAbUlEQVQI122NsQqAMBBD+///JhYEK7Y9q1AHO/Tsoi5GjoqT8IbkLiHqNgbewzmEgHkGEcbxFdMkLyKx1mJZLqKD6BiGM4Rz25TU+h5tK50Ysa5gxr7/8N1LqUJJumkErdF1MpXSG/0l57vC/AA5sacxg0kq+AAAAABJRU5ErkJggg=='); background-size: cover; display: block;"> <img class="gatsby-resp-image-image" style="width: 100%; height: 100%; margin: 0; vertical-align: middle; position: absolute; top: 0; left: 0; box-shadow: inset 0px 0px 0px 400px white;" alt="Error caught by Error Boundary component" title="" src="/static/f1276837b03821b43358d44c14072945/1e088/error-boundaries-stack-trace.png" srcset="/static/f1276837b03821b43358d44c14072945/65ed1/error-boundaries-stack-trace.png 210w, /static/f1276837b03821b43358d44c14072945/d10fb/error-boundaries-stack-trace.png 420w, /static/f1276837b03821b43358d44c14072945/1e088/error-boundaries-stack-trace.png 840w, /static/f1276837b03821b43358d44c14072945/78612/error-boundaries-stack-trace.png 1260w, /static/f1276837b03821b43358d44c14072945/c3a47/error-boundaries-stack-trace.png 1601w" sizes="(max-width: 840px) 100vw, 840px"> </span> </span> </a> <p>You can also see the filenames and line numbers in the component stack trace. This works by default in <a href="https://github.com/facebookincubator/create-react-app" target="_blank" rel="nofollow noopener noreferrer">Create React App</a> projects:</p> <a class="gatsby-resp-image-link" href="/static/45611d4fdbd152829b28ae2348d6dcba/6dd26/error-boundaries-stack-trace-line-numbers.png" style="display: block" target="_blank" rel="noopener"> <span class="gatsby-resp-image-wrapper" style="position: relative; display: block; max-width: 840px; margin-left: auto; margin-right: auto;"> <span class="gatsby-resp-image-background-image" style="padding-bottom: 16.666666666666664%; position: relative; bottom: 0; left: 0; background-image: url('data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABQAAAADCAIAAAAcOLh5AAAACXBIWXMAABYlAAAWJQFJUiTwAAAAdUlEQVQI112NOQqAMBREc/+LWWhhE8RoNkXRKksRbczId0EQXjG8GRh2NA2kRN/DWkIpCIFhgNaUtSZpDA3GcZcyKZWE2IzZ1pWh68A56prqecayIEaE8OeWMT5ckmGaUJYoClQV2pY+nfvw/uHK2bn8Vtn7E0WCp0eQIx0TAAAAAElFTkSuQmCC'); background-size: cover; display: block;"> <img class="gatsby-resp-image-image" style="width: 100%; height: 100%; margin: 0; vertical-align: middle; position: absolute; top: 0; left: 0; box-shadow: inset 0px 0px 0px 400px white;" alt="Error caught by Error Boundary component with line numbers" title="" src="/static/45611d4fdbd152829b28ae2348d6dcba/1e088/error-boundaries-stack-trace-line-numbers.png" srcset="/static/45611d4fdbd152829b28ae2348d6dcba/65ed1/error-boundaries-stack-trace-line-numbers.png 210w, /static/45611d4fdbd152829b28ae2348d6dcba/d10fb/error-boundaries-stack-trace-line-numbers.png 420w, /static/45611d4fdbd152829b28ae2348d6dcba/1e088/error-boundaries-stack-trace-line-numbers.png 840w, /static/45611d4fdbd152829b28ae2348d6dcba/78612/error-boundaries-stack-trace-line-numbers.png 1260w, /static/45611d4fdbd152829b28ae2348d6dcba/6dd26/error-boundaries-stack-trace-line-numbers.png 1597w" sizes="(max-width: 840px) 100vw, 840px"> </span> </span> </a> <p>If you don’t use Create React App, you can add <a href="https://www.npmjs.com/package/@babel/plugin-transform-react-jsx-source" target="_blank" rel="nofollow noopener noreferrer">this plugin</a> manually to your Babel configuration. Note that it’s intended only for development and <strong>must be disabled in production</strong>.</p> <blockquote> <p>Note</p> <p>Component names displayed in the stack traces depend on the <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/name" target="_blank" rel="nofollow noopener noreferrer"><code class="gatsby-code-text">Function.name</code></a> property. If you support older browsers and devices which may not yet provide this natively (e.g. IE 11), consider including a <code class="gatsby-code-text">Function.name</code> polyfill in your bundled application, such as <a href="https://github.com/JamesMGreene/Function.name" target="_blank" rel="nofollow noopener noreferrer"><code class="gatsby-code-text">function.name-polyfill</code></a>. Alternatively, you may explicitly set the <a href="/docs/react-component.html#displayname"><code class="gatsby-code-text">displayName</code></a> property on all your components.</p> </blockquote> <h2 id="how-about-trycatch"><a href="#how-about-trycatch" aria-hidden class="anchor"><svg 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>How About try/catch? </h2> <p><code class="gatsby-code-text">try</code> / <code class="gatsby-code-text">catch</code> is great but it only works for imperative code:</p> <div class="gatsby-highlight" data-language="jsx"><pre class="gatsby-code-jsx"><code class="gatsby-code-jsx"><span class="token keyword">try</span> <span class="token punctuation">{</span> <span class="token function">showButton</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token punctuation">}</span> <span class="token keyword">catch</span> <span class="token punctuation">(</span>error<span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token comment">// ...</span> <span class="token punctuation">}</span></code></pre></div> <p>However, React components are declarative and specify <em>what</em> should be rendered:</p> <div class="gatsby-highlight" data-language="jsx"><pre class="gatsby-code-jsx"><code class="gatsby-code-jsx"><span class="token tag"><span class="token tag"><span class="token punctuation"><</span><span class="token class-name">Button</span></span> <span class="token punctuation">/></span></span></code></pre></div> <p>Error boundaries preserve the declarative nature of React, and behave as you would expect. For example, even if an error occurs in a <code class="gatsby-code-text">componentDidUpdate</code> method caused by a <code class="gatsby-code-text">setState</code> somewhere deep in the tree, it will still correctly propagate to the closest error boundary.</p> <h2 id="how-about-event-handlers"><a href="#how-about-event-handlers" aria-hidden class="anchor"><svg 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>How About Event Handlers? </h2> <p>Error boundaries <strong>do not</strong> catch errors inside event handlers.</p> <p>React doesn’t need error boundaries to recover from errors in event handlers. Unlike the render method and lifecycle methods, the event handlers don’t happen during rendering. So if they throw, React still knows what to display on the screen.</p> <p>If you need to catch an error inside an event handler, use the regular JavaScript <code class="gatsby-code-text">try</code> / <code class="gatsby-code-text">catch</code> statement:</p> <div class="gatsby-highlight has-highlighted-lines" data-language="jsx"><pre class="gatsby-code-jsx"><code class="gatsby-code-jsx"><span class="token keyword">class</span> <span class="token class-name">MyComponent</span> <span class="token keyword">extends</span> <span class="token class-name">React<span class="token punctuation">.</span>Component</span> <span class="token punctuation">{</span> <span class="token function">constructor</span><span class="token punctuation">(</span><span class="token parameter">props</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token keyword">super</span><span class="token punctuation">(</span>props<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token keyword">this</span><span class="token punctuation">.</span>state <span class="token operator">=</span> <span class="token punctuation">{</span> <span class="token literal-property property">error</span><span class="token operator">:</span> <span class="token keyword">null</span> <span class="token punctuation">}</span><span class="token punctuation">;</span> <span class="token keyword">this</span><span class="token punctuation">.</span>handleClick <span class="token operator">=</span> <span class="token keyword">this</span><span class="token punctuation">.</span><span class="token function">handleClick</span><span class="token punctuation">.</span><span class="token function">bind</span><span class="token punctuation">(</span><span class="token keyword">this</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token punctuation">}</span> <span class="token function">handleClick</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="gatsby-highlight-code-line"> <span class="token keyword">try</span> <span class="token punctuation">{</span></span><span class="gatsby-highlight-code-line"> <span class="token comment">// Do something that could throw</span></span><span class="gatsby-highlight-code-line"> <span class="token punctuation">}</span> <span class="token keyword">catch</span> <span class="token punctuation">(</span>error<span class="token punctuation">)</span> <span class="token punctuation">{</span></span><span class="gatsby-highlight-code-line"> <span class="token keyword">this</span><span class="token punctuation">.</span><span class="token function">setState</span><span class="token punctuation">(</span><span class="token punctuation">{</span> error <span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span></span><span class="gatsby-highlight-code-line"> <span class="token punctuation">}</span></span> <span class="token punctuation">}</span> <span class="token function">render</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="gatsby-highlight-code-line"> <span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token keyword">this</span><span class="token punctuation">.</span>state<span class="token punctuation">.</span>error<span class="token punctuation">)</span> <span class="token punctuation">{</span></span><span class="gatsby-highlight-code-line"> <span class="token keyword">return</span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>h1</span><span class="token punctuation">></span></span><span class="token plain-text">Caught an error.</span><span class="token tag"><span class="token tag"><span class="token punctuation"></</span>h1</span><span class="token punctuation">></span></span></span><span class="gatsby-highlight-code-line"> <span class="token punctuation">}</span></span><span class="gatsby-highlight-code-line"> <span class="token keyword">return</span> <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>button</span> <span class="token attr-name">onClick</span><span class="token script language-javascript"><span class="token script-punctuation punctuation">=</span><span class="token punctuation">{</span><span class="token keyword">this</span><span class="token punctuation">.</span>handleClick<span class="token punctuation">}</span></span><span class="token punctuation">></span></span><span class="token plain-text">Click Me</span><span class="token tag"><span class="token tag"><span class="token punctuation"></</span>button</span><span class="token punctuation">></span></span></span> <span class="token punctuation">}</span> <span class="token punctuation">}</span></code></pre></div> <p>Note that the above example is demonstrating regular JavaScript behavior and doesn’t use error boundaries.</p> <h2 id="naming-changes-from-react-15"><a href="#naming-changes-from-react-15" aria-hidden class="anchor"><svg 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>Naming Changes from React 15 </h2> <p>React 15 included a very limited support for error boundaries under a different method name: <code class="gatsby-code-text">unstable_handleError</code>. This method no longer works, and you will need to change it to <code class="gatsby-code-text">componentDidCatch</code> in your code starting from the first 16 beta release.</p> <p>For this change, we’ve provided a <a href="https://github.com/reactjs/react-codemod#error-boundaries" target="_blank" rel="nofollow noopener noreferrer">codemod</a> to automatically migrate your code.</p></div><div class="css-1m173d1"><span class="css-11xil2b"><span>Is this page useful?<button aria-label="Yes" class="css-1k9fay3"><svg focusable="false" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 81.13 89.76" class="css-15scox9"><path d="M22.9 6a18.57 18.57 0 002.67 8.4 25.72 25.72 0 008.65 7.66c3.86 2 8.67 7.13 13.51 11 3.86 3.11 8.57 7.11 11.54 8.45s13.59.26 14.64 1.17c1.88 1.63 1.55 9-.11 15.25-1.61 5.86-5.96 10.55-6.48 16.86-.4 4.83-2.7 4.88-10.93 4.88h-1.35c-3.82 0-8.24 2.93-12.92 3.62a68 68 0 01-9.73.5c-3.57 0-7.86-.08-13.25-.08-3.56 0-4.71-1.83-4.71-4.48h8.42a3.51 3.51 0 000-7H12.28a2.89 2.89 0 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aria-controls="section_000023267459280007508" class="css-1j8jxus"><div class="css-hg8mt2">Installation<svg viewBox="0 0 926.23699 573.74994" version="1.1" x="0px" y="0px" width="10" height="10" class="css-1jiuhrf"><g transform="translate(904.92214,-879.1482)"><path d=" m -673.67664,1221.6502 -231.2455,-231.24803 55.6165, -55.627 c 30.5891,-30.59485 56.1806,-55.627 56.8701,-55.627 0.6894, 0 79.8637,78.60862 175.9427,174.68583 l 174.6892,174.6858 174.6892, -174.6858 c 96.079,-96.07721 175.253196,-174.68583 175.942696, -174.68583 0.6895,0 26.281,25.03215 56.8701, 55.627 l 55.6165,55.627 -231.245496,231.24803 c -127.185,127.1864 -231.5279,231.248 -231.873,231.248 -0.3451,0 -104.688, -104.0616 -231.873,-231.248 z " fill="currentColor"></path></g></svg></div></button><ul id="section_000023267459280007508" class="css-14d3mgr"><li class="css-atv6j6"><a class="css-e8rm5m" href="/docs/getting-started.html">Getting Started</a></li><li class="css-atv6j6"><a class="css-e8rm5m" href="/docs/add-react-to-a-website.html">Add React to a Website</a></li><li class="css-atv6j6"><a class="css-e8rm5m" href="/docs/create-a-new-react-app.html">Create a New React App</a></li><li class="css-atv6j6"><a class="css-e8rm5m" href="/docs/cdn-links.html">CDN Links</a></li><li class="css-atv6j6"><a class="css-e8rm5m" href="/docs/release-channels.html">Release Channels</a></li></ul></div><div><button aria-expanded="false" aria-controls="section_044650970003899193" class="css-1j8jxus"><div class="css-hg8mt2">Main Concepts<svg viewBox="0 0 926.23699 573.74994" version="1.1" x="0px" y="0px" width="10" height="10" class="css-1jiuhrf"><g transform="translate(904.92214,-879.1482)"><path d=" m -673.67664,1221.6502 -231.2455,-231.24803 55.6165, -55.627 c 30.5891,-30.59485 56.1806,-55.627 56.8701,-55.627 0.6894, 0 79.8637,78.60862 175.9427,174.68583 l 174.6892,174.6858 174.6892, -174.6858 c 96.079,-96.07721 175.253196,-174.68583 175.942696, -174.68583 0.6895,0 26.281,25.03215 56.8701, 55.627 l 55.6165,55.627 -231.245496,231.24803 c -127.185,127.1864 -231.5279,231.248 -231.873,231.248 -0.3451,0 -104.688, -104.0616 -231.873,-231.248 z " fill="currentColor"></path></g></svg></div></button><ul id="section_044650970003899193" class="css-14d3mgr"><li class="css-atv6j6"><a class="css-e8rm5m" href="/docs/hello-world.html">1. 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