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66 lines
6.7 KiB
HTML
66 lines
6.7 KiB
HTML
<article class="" id="post-">
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<header class="entry-header">
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<h1 class="entry-title">:first Selector</h1>
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<div class="entry-meta">
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所属分类：<span class="category"><a href="/category/selectors/">选择器</a> > <a href="/category/selectors/basic-filter-selectors/">基础过滤</a></span><span class="category-divider"> | </span><span class="category"><a href="/category/selectors/">选择器</a> > <a href="/category/selectors/jquery-selector-extensions/">jQuery 扩展</a></span>
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<span class="pull-right">英文文档：<a href="https://api.jquery123.com/first-selector/" target="_blank">:first Selector</a></span>
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</div><!-- .entry-meta -->
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</header><!-- .entry-header -->
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<!-- .entry-header -->
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<div class="entry-content">
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<article class="entry selector" id="first1"><h2 class="section-title"><span>first selector</span></h2>
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<div class="entry-wrapper">
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<p class="desc"><strong>描述: </strong>选择第一个匹配的元素。</p>
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<ul class="signatures"><li class="signature"><h4 class="name">
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<span class="version-details">添加的版本: <a href="/category/version/1.0/">1.0</a></span>jQuery( ":first" )</h4></li></ul>
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<div class="longdesc" id="entry-longdesc">
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<p><code>:first</code>伪类选择器相当于<code>:eq(0)</code>。它也可以写为<code>:lt(1)</code>。虽然<a href="/first-selector">:first</a>只匹配一个单独的元素，但是<code>:first-child</code>选择器可以匹配多个：即为每个父级元素匹配第一个子元素。</p>
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</div>
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<h3>Additional Notes（其他注意事项）:</h3>
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<div class="longdesc"><ul>
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<li>
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因为 <code>:first()</code> 是一个 jQuery 延伸出来的一个选择器。 并且不是的CSS规范的一部分, 使用<code>:first()</code>查询不能充分利用原生DOM提供的<code>querySelectorAll()</code> 方法来提高性能。为了在现代浏览器上获得更佳的性能，请使用<a href="/filter"><code>.filter(":first")</code></a>代替。
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</li>
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<li>
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被选中的元素按照他们在文档中出现的顺序。 </li>
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</ul></div>
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<section class="entry-examples" id="entry-examples"><header><h2 class="underline">例子:</h2></header><div class="entry-example" id="example-0">
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<h4><span class="desc">查找第一个表行。</span></h4>
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<div class="syntaxhighlighter xml ">
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<table>
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<tbody>
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<tr>
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<td class="gutter">
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<div class="line n1">1</div>
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<div class="line n2">2</div>
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<div class="line n3">3</div>
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<div class="line n4">4</div>
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<div class="line n5">5</div>
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<div class="line n6">6</div>
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<div class="line n7">7</div>
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<div class="line n8">8</div>
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<div class="line n9">9</div>
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<div class="line n10">10</div>
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<div class="line n11">11</div>
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<div class="line n12">12</div>
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<div class="line n14">14</div>
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<div class="line n15">15</div>
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<div class="line n16">16</div>
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<div class="line n17">17</div>
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<div class="line n18">18</div>
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<div class="line n19">19</div>
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<div class="line n20">20</div>
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</td>
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<td class="code">
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<pre><div class="container"><div class="line"><code><span class="doctype"><!DOCTYPE html></span></code></div></div><div class="container"><div class="line"><code><span class="tag"><<span class="title">html</span>></span></code></div></div><div class="container"><div class="line"><code><span class="tag"><<span class="title">head</span>></span></code></div></div><div class="container"><div class="line"><code> <span class="tag"><<span class="title">style</span>></span><span class="css"></span></code></div></div><div class="container"><div class="line"><code> </code></div></div><div class="container"><div class="line"><code> <span class="tag">td</span> <span class="rules">{ <span class="rule"><span class="attribute">color</span>:<span class="value">blue;</span></span> <span class="rule"><span class="attribute">font-weight</span>:<span class="value">bold;</span></span> <span class="rule">}</span></span></code></div></div><div class="container"><div class="line"><code> <span class="tag"></<span class="title">style</span>></span></code></div></div><div class="container"><div class="line"><code> <span class="tag"><<span class="title">script</span> <span class="attribute">src</span>=<span class="value">"https://code.jquery.com/jquery-latest.js"</span>></span><span class="javascript"></span><span class="tag"></<span class="title">script</span>></span></code></div></div><div class="container"><div class="line"><code><span class="tag"></<span class="title">head</span>></span></code></div></div><div class="container"><div class="line"><code><span class="tag"><<span class="title">body</span>></span></code></div></div><div class="container"><div class="line"><code> <span class="tag"><<span class="title">table</span>></span></code></div></div><div class="container"><div class="line"><code> <span class="tag"><<span class="title">tr</span>></span><span class="tag"><<span class="title">td</span>></span>Row 1<span class="tag"></<span class="title">td</span>></span><span class="tag"></<span class="title">tr</span>></span></code></div></div><div class="container"><div class="line"><code> <span class="tag"><<span class="title">tr</span>></span><span class="tag"><<span class="title">td</span>></span>Row 2<span class="tag"></<span class="title">td</span>></span><span class="tag"></<span class="title">tr</span>></span></code></div></div><div class="container"><div class="line"><code> </code></div></div><div class="container"><div class="line"><code> <span class="tag"><<span class="title">tr</span>></span><span class="tag"><<span class="title">td</span>></span>Row 3<span class="tag"></<span class="title">td</span>></span><span class="tag"></<span class="title">tr</span>></span></code></div></div><div class="container"><div class="line"><code> <span class="tag"></<span class="title">table</span>></span></code></div></div><div class="container"><div class="line"><code><span class="tag"><<span class="title">script</span>></span><span class="javascript">$(<span class="string">"tr:first"</span>).css(<span class="string">"font-style"</span>, <span class="string">"italic"</span>);</span><span class="tag"></<span class="title">script</span>></span></code></div></div><div class="container"><div class="line"><code> </code></div></div><div class="container"><div class="line"><code><span class="tag"></<span class="title">body</span>></span></code></div></div><div class="container"><div class="line"><code><span class="tag"></<span class="title">html</span>></span></code></div></div></pre>
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</td>
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</tr>
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</tbody>
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</table>
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</div>
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<h4>Demo:</h4>
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<div class="demo code-demo"></div>
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</div></section>
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</div></article> </div>
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</article> |