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Paul O’Shannessy
498 lines
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HTML
498 lines
19 KiB
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<a href="/react/tips/false-in-jsx.html">False in JSX</a>
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<a href="/react/tips/use-react-with-other-libraries.html">Use React with Other Libraries</a>
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<a href="/react/tips/dangerously-set-inner-html.html">Dangerously Set innerHTML</a>
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</div>
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</div>
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<div class="inner-content">
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<h1>
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JSX 展开属性
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<a class="edit-page-link" href="https://github.com/facebook/react/tree/master/docs/docs/02.2-jsx-spread.zh-CN.md" target="_blank">Edit on GitHub</a>
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</h1>
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<div class="subHeader"></div>
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<p>如果你事先知道组件需要的全部 Props（属性），JSX 很容易地这样写：</p>
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<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"> <span class="kd">var</span> <span class="nx">component</span> <span class="o">=</span> <span class="o"><</span><span class="nx">Component</span> <span class="nx">foo</span><span class="o">=</span><span class="p">{</span><span class="nx">x</span><span class="p">}</span> <span class="nx">bar</span><span class="o">=</span><span class="p">{</span><span class="nx">y</span><span class="p">}</span> <span class="o">/></span><span class="p">;</span>
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</code></pre></div><h2><a class="anchor" name="-props-"></a>修改 Props 是不好的，明白吗 <a class="hash-link" href="#-props-">#</a></h2>
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<p>如果你不知道要设置哪些 Props，那么现在最好不要设置它：</p>
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<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"> <span class="kd">var</span> <span class="nx">component</span> <span class="o">=</span> <span class="o"><</span><span class="nx">Component</span> <span class="o">/></span><span class="p">;</span>
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<span class="nx">component</span><span class="p">.</span><span class="nx">props</span><span class="p">.</span><span class="nx">foo</span> <span class="o">=</span> <span class="nx">x</span><span class="p">;</span> <span class="c1">// 不好</span>
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<span class="nx">component</span><span class="p">.</span><span class="nx">props</span><span class="p">.</span><span class="nx">bar</span> <span class="o">=</span> <span class="nx">y</span><span class="p">;</span> <span class="c1">// 同样不好</span>
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</code></pre></div>
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<p>这样是反模式，因为 React 不能帮你检查属性类型（propTypes）。这样即使你的 属性类型有错误也不能得到清晰的错误提示。</p>
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<p>Props 应该被认为是不可变的。在别处修改 props 对象可能会导致预料之外的结果，所以原则上这将是一个冻结的对象。</p>
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<h2><a class="anchor" name="spread-attributes"></a>展开属性（Spread Attributes） <a class="hash-link" href="#spread-attributes">#</a></h2>
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<p>现在你可以使用 JSX 的新特性 - 展开属性：</p>
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<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"> <span class="kd">var</span> <span class="nx">props</span> <span class="o">=</span> <span class="p">{};</span>
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<span class="nx">props</span><span class="p">.</span><span class="nx">foo</span> <span class="o">=</span> <span class="nx">x</span><span class="p">;</span>
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<span class="nx">props</span><span class="p">.</span><span class="nx">bar</span> <span class="o">=</span> <span class="nx">y</span><span class="p">;</span>
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<span class="kd">var</span> <span class="nx">component</span> <span class="o">=</span> <span class="o"><</span><span class="nx">Component</span> <span class="p">{...</span><span class="nx">props</span><span class="p">}</span> <span class="o">/></span><span class="p">;</span>
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</code></pre></div>
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<p>传入对象的属性会被复制到组件内。</p>
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<p>它能被多次使用，也可以和其它属性一起用。注意顺序很重要，后面的会覆盖掉前面的。</p>
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<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"> <span class="kd">var</span> <span class="nx">props</span> <span class="o">=</span> <span class="p">{</span> <span class="nx">foo</span><span class="o">:</span> <span class="s1">'default'</span> <span class="p">};</span>
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<span class="kd">var</span> <span class="nx">component</span> <span class="o">=</span> <span class="o"><</span><span class="nx">Component</span> <span class="p">{...</span><span class="nx">props</span><span class="p">}</span> <span class="nx">foo</span><span class="o">=</span><span class="p">{</span><span class="s1">'override'</span><span class="p">}</span> <span class="o">/></span><span class="p">;</span>
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<span class="nx">console</span><span class="p">.</span><span class="nx">log</span><span class="p">(</span><span class="nx">component</span><span class="p">.</span><span class="nx">props</span><span class="p">.</span><span class="nx">foo</span><span class="p">);</span> <span class="c1">// 'override'</span>
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</code></pre></div><h2><a class="anchor" name="-...-"></a>这个奇怪的 <code>...</code> 标记是什么？ <a class="hash-link" href="#-...-">#</a></h2>
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<p>这个 <code>...</code> 操作符（增强的操作符）已经被 <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Spread_operator">ES6 数组</a> 支持。相关的还有 ECMAScript 规范草案中的 <a href="https://github.com/sebmarkbage/ecmascript-rest-spread">Object 剩余和展开属性（Rest and Spread Properties）</a>。我们利用了这些还在制定中标准中已经被支持的特性来使 JSX 拥有更优雅的语法。</p>
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<div class="docs-prevnext">
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