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Dan Abramov
206 lines
14 KiB
HTML
206 lines
14 KiB
HTML
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<!DOCTYPE html>
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<head>
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<meta charset="utf-8">
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<meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">
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<title>Unknown Prop Warning - React</title>
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<meta property="og:title" content="Unknown Prop Warning - React">
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React
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<ul class="nav-site nav-site-internal">
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<li><a href="/react/docs/hello-world.html">Docs</a></li>
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<li><a href="/react/tutorial/tutorial.html">Tutorial</a></li>
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<li><a href="/react/community/support.html">Community</a></li>
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<section class="content wrap documentationContent nosidebar">
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<div class="inner-content">
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<h1>Unknown Prop Warning</h1>
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<div class="subHeader"></div>
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<p>The unknown-prop warning will fire if you attempt to render a DOM element with a prop that is not recognized by React as a legal DOM attribute/property. You should ensure that your DOM elements do not have spurious props floating around.</p>
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<p>There are a couple of likely reasons this warning could be appearing:</p>
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<ol>
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<li><p>Are you using <code>{...this.props}</code> or <code>cloneElement(element, this.props)</code>? Your component is transferring its own props directly to a child element (eg. https://facebook.github.io/react/docs/transferring-props.html). When transferring props to a child component, you should ensure that you are not accidentally forwarding props that were intended to be interpreted by the parent component.</p></li>
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<li><p>You are using a non-standard DOM attribute on a native DOM node, perhaps to represent custom data. If you are trying to attach custom data to a standard DOM element, consider using a custom data attribute as described <a href="https://developer.mozilla.org/en-US/docs/Web/Guide/HTML/Using_data_attributes">on MDN</a>.</p></li>
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<li><p>React does not yet recognize the attribute you specified. This will likely be fixed in a future version of React. However, React currently strips all unknown attributes, so specifying them in your React app will not cause them to be rendered.</p></li>
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<li><p>You are using a React component without an upper case. React interprets it as a DOM tag because <a href="/react/docs/jsx-in-depth.html#user-defined-components-must-be-capitalized">React JSX transform uses the upper vs. lower case convention to distinguish between user-defined components and DOM tags</a>.</p></li>
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</ol>
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<hr>
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<p>To fix this, composite components should "consume" any prop that is intended for the composite component and not intended for the child component. Example:</p>
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<p><strong>Bad:</strong> Unexpected <code>layout</code> prop is forwarded to the <code>div</code> tag.</p>
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<div class="highlight"><pre><code class="language-js" data-lang="js"><span class="kd">function</span> <span class="nx">MyDiv</span><span class="p">(</span><span class="nx">props</span><span class="p">)</span> <span class="p">{</span>
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<span class="k">if</span> <span class="p">(</span><span class="nx">props</span><span class="p">.</span><span class="nx">layout</span> <span class="o">===</span> <span class="s1">'horizontal'</span><span class="p">)</span> <span class="p">{</span>
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<span class="c1">// BAD! Because you know for sure "layout" is not a prop that <div> understands.</span>
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<span class="k">return</span> <span class="o"><</span><span class="nx">div</span> <span class="p">{...</span><span class="nx">props</span><span class="p">}</span> <span class="nx">style</span><span class="o">=</span><span class="p">{</span><span class="nx">getHorizontalStyle</span><span class="p">()}</span> <span class="o">/></span>
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<span class="p">}</span> <span class="k">else</span> <span class="p">{</span>
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<span class="c1">// BAD! Because you know for sure "layout" is not a prop that <div> understands.</span>
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<span class="k">return</span> <span class="o"><</span><span class="nx">div</span> <span class="p">{...</span><span class="nx">props</span><span class="p">}</span> <span class="nx">style</span><span class="o">=</span><span class="p">{</span><span class="nx">getVerticalStyle</span><span class="p">()}</span> <span class="o">/></span>
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<span class="p">}</span>
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<span class="p">}</span>
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</code></pre></div>
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<p><strong>Good:</strong> The spread operator can be used to pull variables off props, and put the remaining props into a variable.</p>
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<div class="highlight"><pre><code class="language-js" data-lang="js"><span class="kd">function</span> <span class="nx">MyDiv</span><span class="p">(</span><span class="nx">props</span><span class="p">)</span> <span class="p">{</span>
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<span class="kr">const</span> <span class="p">{</span> <span class="nx">layout</span><span class="p">,</span> <span class="p">...</span><span class="nx">rest</span> <span class="p">}</span> <span class="o">=</span> <span class="nx">props</span>
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<span class="k">if</span> <span class="p">(</span><span class="nx">layout</span> <span class="o">===</span> <span class="s1">'horizontal'</span><span class="p">)</span> <span class="p">{</span>
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<span class="k">return</span> <span class="o"><</span><span class="nx">div</span> <span class="p">{...</span><span class="nx">rest</span><span class="p">}</span> <span class="nx">style</span><span class="o">=</span><span class="p">{</span><span class="nx">getHorizontalStyle</span><span class="p">()}</span> <span class="o">/></span>
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<span class="p">}</span> <span class="k">else</span> <span class="p">{</span>
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<span class="k">return</span> <span class="o"><</span><span class="nx">div</span> <span class="p">{...</span><span class="nx">rest</span><span class="p">}</span> <span class="nx">style</span><span class="o">=</span><span class="p">{</span><span class="nx">getVerticalStyle</span><span class="p">()}</span> <span class="o">/></span>
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<span class="p">}</span>
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<span class="p">}</span>
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</code></pre></div>
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<p><strong>Good:</strong> You can also assign the props to a new object and delete the keys that you're using from the new object. Be sure not to delete the props from the original <code>this.props</code> object, since that object should be considered immutable.</p>
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<div class="highlight"><pre><code class="language-js" data-lang="js"><span class="kd">function</span> <span class="nx">MyDiv</span><span class="p">(</span><span class="nx">props</span><span class="p">)</span> <span class="p">{</span>
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<span class="kr">const</span> <span class="nx">divProps</span> <span class="o">=</span> <span class="nb">Object</span><span class="p">.</span><span class="nx">assign</span><span class="p">({},</span> <span class="nx">props</span><span class="p">);</span>
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<span class="k">delete</span> <span class="nx">divProps</span><span class="p">.</span><span class="nx">layout</span><span class="p">;</span>
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<span class="k">if</span> <span class="p">(</span><span class="nx">props</span><span class="p">.</span><span class="nx">layout</span> <span class="o">===</span> <span class="s1">'horizontal'</span><span class="p">)</span> <span class="p">{</span>
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<span class="k">return</span> <span class="o"><</span><span class="nx">div</span> <span class="p">{...</span><span class="nx">divProps</span><span class="p">}</span> <span class="nx">style</span><span class="o">=</span><span class="p">{</span><span class="nx">getHorizontalStyle</span><span class="p">()}</span> <span class="o">/></span>
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<span class="p">}</span> <span class="k">else</span> <span class="p">{</span>
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<span class="k">return</span> <span class="o"><</span><span class="nx">div</span> <span class="p">{...</span><span class="nx">divProps</span><span class="p">}</span> <span class="nx">style</span><span class="o">=</span><span class="p">{</span><span class="nx">getVerticalStyle</span><span class="p">()}</span> <span class="o">/></span>
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<span class="p">}</span>
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<span class="p">}</span>
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</code></pre></div>
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