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Dan Abramov
617 lines
29 KiB
HTML
617 lines
29 KiB
HTML
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<title>表单组件 | React</title>
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<a href="/react/contributing/how-to-contribute.html">How to Contribute</a>
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<a href="/react/contributing/codebase-overview.html">Codebase Overview</a>
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<a href="/react/contributing/design-principles.html">Design Principles</a>
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<div class="inner-content">
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<a class="edit-page-link" href="https://github.com/facebook/react/tree/master/docs/docs/07-forms.zh-CN.md" target="_blank">Edit on GitHub</a>
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<h1>
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表单组件
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</h1>
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<div class="subHeader"></div>
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<p>诸如 <code><input></code>、<code><textarea></code>、<code><option></code> 这样的表单组件不同于其他原生组件，因为他们可以通过用户交互发生变化。这些组件提供的界面使响应用户交互的表单数据处理更加容易。</p>
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<p>关于 <code><form></code> 事件详情请查看 <a href="/react/docs/events-zh-CN.html#%E8%A1%A8%E5%8D%95%E4%BA%8B%E4%BB%B6">表单事件</a>。</p>
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<h2><a class="anchor" name="交互属性"></a>交互属性 <a class="hash-link" href="#交互属性">#</a></h2>
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<p>表单组件支持几个受用户交互影响的属性：</p>
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<ul>
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<li><code>value</code>，用于 <code><input></code>、<code><textarea></code> 组件。</li>
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<li><code>checked</code>，用于类型为 <code>checkbox</code> 或者 <code>radio</code> 的 <code><input></code> 组件。</li>
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<li><code>selected</code>，用于 <code><option></code> 组件。</li>
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</ul>
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<p>在 HTML 中，<code><textarea></code> 的值通过子节点设置；在 React 中则应该使用 <code>value</code> 代替。</p>
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<p>表单组件可以通过 <code>onChange</code> 回调函数来监听组件变化。当用户做出以下交互时，<code>onChange</code> 执行并通过浏览器做出响应：</p>
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<ul>
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<li><code><input></code> 或 <code><textarea></code> 的 <code>value</code> 发生变化时。</li>
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<li><code><input></code> 的 <code>checked</code> 状态改变时。</li>
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<li><code><option></code> 的 <code>selected</code> 状态改变时。</li>
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</ul>
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<p>和所有 DOM 事件一样，所有的 HTML 原生组件都支持 <code>onChange</code> 属性，而且可以用来监听冒泡的 <code>change</code> 事件。</p>
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<blockquote>
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<p>注意:</p>
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<p>对于 <code><input></code> and <code><textarea></code>， <code>onChange</code> 取代 — 一般应该用来替代 — DOM内建的 <a href="https://developer.mozilla.org/en-US/docs/Web/API/GlobalEventHandlers/oninput"><code>oninput</code></a> 事件处理。</p>
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</blockquote>
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<h2><a class="anchor" name="受控组件"></a>受控组件 <a class="hash-link" href="#受控组件">#</a></h2>
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<p>一个<em>受控</em>的 <code><input></code> 有一个 <code>value</code> prop。渲染一个受控 <code><input></code> 会反映 <code>value</code> prop 的值。</p>
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<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"> <span class="nx">render</span><span class="o">:</span> <span class="kd">function</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">input</span> <span class="nx">type</span><span class="o">=</span><span class="s2">"text"</span> <span class="nx">value</span><span class="o">=</span><span class="s2">"Hello!"</span> <span class="o">/></span><span class="p">;</span>
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<span class="p">}</span>
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</code></pre></div>
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<p>用户输入在被渲染的元素里将没有作用,因为 React 已经声明值为 <code>Hello!</code>。要更新 value 来响应用户输入，你可以使用 <code>onChange</code> 事件：</p>
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<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"> <span class="nx">getInitialState</span><span class="o">:</span> <span class="kd">function</span><span class="p">()</span> <span class="p">{</span>
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<span class="k">return</span> <span class="p">{</span><span class="nx">value</span><span class="o">:</span> <span class="s1">'Hello!'</span><span class="p">};</span>
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<span class="p">},</span>
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<span class="nx">handleChange</span><span class="o">:</span> <span class="kd">function</span><span class="p">(</span><span class="nx">event</span><span class="p">)</span> <span class="p">{</span>
|
||
<span class="k">this</span><span class="p">.</span><span class="nx">setState</span><span class="p">({</span><span class="nx">value</span><span class="o">:</span> <span class="nx">event</span><span class="p">.</span><span class="nx">target</span><span class="p">.</span><span class="nx">value</span><span class="p">});</span>
|
||
<span class="p">},</span>
|
||
<span class="nx">render</span><span class="o">:</span> <span class="kd">function</span><span class="p">()</span> <span class="p">{</span>
|
||
<span class="k">return</span> <span class="p">(</span>
|
||
<span class="o"><</span><span class="nx">input</span>
|
||
<span class="nx">type</span><span class="o">=</span><span class="s2">"text"</span>
|
||
<span class="nx">value</span><span class="o">=</span><span class="p">{</span><span class="k">this</span><span class="p">.</span><span class="nx">state</span><span class="p">.</span><span class="nx">value</span><span class="p">}</span>
|
||
<span class="nx">onChange</span><span class="o">=</span><span class="p">{</span><span class="k">this</span><span class="p">.</span><span class="nx">handleChange</span><span class="p">}</span>
|
||
<span class="o">/></span>
|
||
<span class="p">);</span>
|
||
<span class="p">}</span>
|
||
</code></pre></div>
|
||
<p>在这个例子中，我们接受用户提供的值并更新 <code><input></code> 组件的 <code>value</code> prop。这个模式使实现响应或者验证用户输入的界面更容易。例如：</p>
|
||
<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"> <span class="nx">handleChange</span><span class="o">:</span> <span class="kd">function</span><span class="p">(</span><span class="nx">event</span><span class="p">)</span> <span class="p">{</span>
|
||
<span class="k">this</span><span class="p">.</span><span class="nx">setState</span><span class="p">({</span><span class="nx">value</span><span class="o">:</span> <span class="nx">event</span><span class="p">.</span><span class="nx">target</span><span class="p">.</span><span class="nx">value</span><span class="p">.</span><span class="nx">substr</span><span class="p">(</span><span class="mi">0</span><span class="p">,</span> <span class="mi">140</span><span class="p">)});</span>
|
||
<span class="p">}</span>
|
||
</code></pre></div>
|
||
<p>上面的代码接受用户输入，并截取前 140 个字符。</p>
|
||
|
||
<p>受控组件不维持一个自己的内部状态;它单纯的基于 props 渲染。</p>
|
||
<h3><a class="anchor" name="复选框与单选按钮的潜在问题"></a>复选框与单选按钮的潜在问题 <a class="hash-link" href="#复选框与单选按钮的潜在问题">#</a></h3>
|
||
<p>当心，在力图标准化复选框与单选按钮的变换处理中，React使用 <code>click</code> 事件代替 <code>change</code> 事件。在大多数情况下它们表现的如同预期，除了在<code>change</code> handler中调用<code>preventDefault</code> 。<code>preventDefault</code> 阻止了浏览器视觉上更新输入，即使<code>checked</code>被触发。变通的方式是要么移除<code>preventDefault</code>的调用，要么把<code>checked</code> 的触发放在一个<code>setTimeout</code>里。</p>
|
||
<h2><a class="anchor" name="不受控组件"></a>不受控组件 <a class="hash-link" href="#不受控组件">#</a></h2>
|
||
<p>一个没有 <code>value</code> 属性的 <code><input></code> 是一个不<em>受控</em>组件:</p>
|
||
<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"> <span class="nx">render</span><span class="o">:</span> <span class="kd">function</span><span class="p">()</span> <span class="p">{</span>
|
||
<span class="k">return</span> <span class="o"><</span><span class="nx">input</span> <span class="nx">type</span><span class="o">=</span><span class="s2">"text"</span> <span class="o">/></span><span class="p">;</span>
|
||
<span class="p">}</span>
|
||
</code></pre></div>
|
||
<p>上面的代码将渲染出一个空值的输入框，用户输入将立即反应到元素上。和受控元素一样，使用 <code>onChange</code> 事件可以监听值的变化。</p>
|
||
|
||
<p><em>不受控</em>组件维持它自己的内部状态。</p>
|
||
<h3><a class="anchor" name="默认值"></a>默认值 <a class="hash-link" href="#默认值">#</a></h3>
|
||
<p>如果想给组件设置一个非空的初始值，可以使用 <code>defaultValue</code> 属性。例如：</p>
|
||
<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"> <span class="nx">render</span><span class="o">:</span> <span class="kd">function</span><span class="p">()</span> <span class="p">{</span>
|
||
<span class="k">return</span> <span class="o"><</span><span class="nx">input</span> <span class="nx">type</span><span class="o">=</span><span class="s2">"text"</span> <span class="nx">defaultValue</span><span class="o">=</span><span class="s2">"Hello!"</span> <span class="o">/></span><span class="p">;</span>
|
||
<span class="p">}</span>
|
||
</code></pre></div>
|
||
<p>这个例子会像上面的 <strong>受控组件</strong> 例子一样运行。</p>
|
||
|
||
<p>同样的， <code><input type="checkbox"></code> 和 <code><input type="radio"></code> 支持 <code>defaultChecked</code> 、 <code><select></code> 支持 <code>defaultValue</code>.</p>
|
||
|
||
<blockquote>
|
||
<p>注意:</p>
|
||
|
||
<p><code>defaultValue</code> 和 <code>defaultChecked</code> props 只能在内部渲染时被使用。 如果你需要在随后的渲染更新值, 你需要使用 <a href="#%E5%8F%97%E6%8E%A7%E7%BB%84%E4%BB%B6">受控组件</a>.</p>
|
||
</blockquote>
|
||
<h2><a class="anchor" name="高级主题"></a>高级主题 <a class="hash-link" href="#高级主题">#</a></h2><h3><a class="anchor" name="为什么使用受控组件"></a>为什么使用受控组件？ <a class="hash-link" href="#为什么使用受控组件">#</a></h3>
|
||
<p>在 React 中使用诸如 <code><input></code> 的表单组件时，遇到了一个在传统 HTML 中没有的挑战。比如下面的代码：</p>
|
||
<div class="highlight"><pre><code class="language-html" data-lang="html"> <span class="nt"><input</span> <span class="na">type=</span><span class="s">"text"</span> <span class="na">name=</span><span class="s">"title"</span> <span class="na">value=</span><span class="s">"Untitled"</span> <span class="nt">/></span>
|
||
</code></pre></div>
|
||
<p>它渲染一个<em>初始值</em>为 <code>Untitled</code> 的输入框。当用户改变输入框的值时，节点的 <code>value</code> 属性( <em>property</em>)将随之变化，但是 <code>node.getAttribute('value')</code> 还是会返回初始设置的值 <code>Untitled</code>.</p>
|
||
|
||
<p>与 HTML 不同，React 组件必须在任何时间点表现视图的状态，而不仅仅是在初始化时。比如在 React 中：</p>
|
||
<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"> <span class="nx">render</span><span class="o">:</span> <span class="kd">function</span><span class="p">()</span> <span class="p">{</span>
|
||
<span class="k">return</span> <span class="o"><</span><span class="nx">input</span> <span class="nx">type</span><span class="o">=</span><span class="s2">"text"</span> <span class="nx">name</span><span class="o">=</span><span class="s2">"title"</span> <span class="nx">value</span><span class="o">=</span><span class="s2">"Untitled"</span> <span class="o">/></span><span class="p">;</span>
|
||
<span class="p">}</span>
|
||
</code></pre></div>
|
||
<p>由于这个方法描述了在任意时间点上的视图，那么文本输入框的值就应该<em>始终</em>为 <code>Untitled</code>。</p>
|
||
<h3><a class="anchor" name="为什么-lttextareagt-使用-value-属性"></a>为什么 <code><textarea></code> 使用 <code>value</code> 属性？ <a class="hash-link" href="#为什么-lttextareagt-使用-value-属性">#</a></h3>
|
||
<p>在 HTML 中， <code><textarea></code> 的值通常使用子节点设置：</p>
|
||
<div class="highlight"><pre><code class="language-html" data-lang="html"> <span class="c"><!-- 反例：在 React 中不要这样使用！ --></span>
|
||
<span class="nt"><textarea</span> <span class="na">name=</span><span class="s">"description"</span><span class="nt">></span>This is the description.<span class="nt"></textarea></span>
|
||
</code></pre></div>
|
||
<p>对 HTML 而言，让开发者设置多行的值很容易。但是，由于 React 是 JavaScript，没有字符串限制，可以使用 <code>\n</code> 实现换行。简言之，React 已经有 <code>value</code>、<code>defaultValue</code> 属性，<code><textarea></code> 组件的子节点扮演什么角色就有点模棱两可了。基于此， 设置 <code><textarea></code> 值时不应该使用子节点：</p>
|
||
<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"> <span class="o"><</span><span class="nx">textarea</span> <span class="nx">name</span><span class="o">=</span><span class="s2">"description"</span> <span class="nx">value</span><span class="o">=</span><span class="s2">"This is a description."</span> <span class="o">/></span>
|
||
</code></pre></div>
|
||
<p>如果 <em>非要</em> 使用子节点，效果和使用 <code>defaultValue</code> 一样。</p>
|
||
<h3><a class="anchor" name="为什么-ltselectgt-使用-value-属性"></a>为什么 <code><select></code> 使用 <code>value</code> 属性 <a class="hash-link" href="#为什么-ltselectgt-使用-value-属性">#</a></h3>
|
||
<p>HTML 中 <code><select></code> 通常使用 <code><option></code> 的 <code>selected</code> 属性设置选中状态；React 为了更方便地控制组件，采用以下方式代替：</p>
|
||
<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"> <span class="o"><</span><span class="nx">select</span> <span class="nx">value</span><span class="o">=</span><span class="s2">"B"</span><span class="o">></span>
|
||
<span class="o"><</span><span class="nx">option</span> <span class="nx">value</span><span class="o">=</span><span class="s2">"A"</span><span class="o">></span><span class="nx">Apple</span><span class="o"><</span><span class="err">/option></span>
|
||
<span class="o"><</span><span class="nx">option</span> <span class="nx">value</span><span class="o">=</span><span class="s2">"B"</span><span class="o">></span><span class="nx">Banana</span><span class="o"><</span><span class="err">/option></span>
|
||
<span class="o"><</span><span class="nx">option</span> <span class="nx">value</span><span class="o">=</span><span class="s2">"C"</span><span class="o">></span><span class="nx">Cranberry</span><span class="o"><</span><span class="err">/option></span>
|
||
<span class="o"><</span><span class="err">/select></span>
|
||
</code></pre></div>
|
||
<p>如果是不受控组件，则使用 <code>defaultValue</code>。</p>
|
||
|
||
<blockquote>
|
||
<p>注意：</p>
|
||
|
||
<p>给 <code>value</code> 属性传递一个数组，可以选中多个选项：<code><select multiple={true} value={['B', 'C']}></code>。</p>
|
||
</blockquote>
|
||
|
||
|
||
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||
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||
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||
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|
||
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|
||
A Facebook & Instagram collaboration.<br>
|
||
<a href="/react/acknowledgements.html">Acknowledgements</a>
|
||
</div>
|
||
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|
||
© 2013–2016 Facebook Inc.<br>
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