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75 lines
7.9 KiB
HTML
75 lines
7.9 KiB
HTML
<article class="" id="post-">
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<header class="entry-header">
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<h1 class="entry-title">:lt() 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/lt-selector/" target="_blank">:lt() 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="lt1"><h2 class="section-title"><span>lt selector</span></h2>
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<div class="entry-wrapper">
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<p class="desc"><strong>描述: </strong>选择匹配集合中所有索引值小于给定<code>index</code>参数的元素。</p>
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<ul class="signatures"><li class="signature">
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<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( ":lt(index)" )</h4>
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<p class="argument"><strong>index: </strong>从 0 开始计数的索引值。</p>
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</li>
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<li class="signature">
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<h4 class="name">
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<span class="version-details">version added: <a href="/category/version/1.8/">1.8</a></span>jQuery( ":lt(-index)" )</h4>
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<p class="argument"><strong>-index: </strong>从0开始计数的索引值。 从最后一个元素开始反向计数。 </p>
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</li></ul>
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<div class="longdesc" id="entry-longdesc">
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<p>
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<strong>index-related selectors（索引相关的选择）</strong>
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</p>
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<p>这种索引相关的选择器（包括这个“小于”选择器）会在先前提供的选择器筛选出的元素基础上再进行筛选。进一步筛选的依据就是这个元素在原先匹配集合中的顺序。举例来说，如果一开始通过 class 选择器 (<code>.myclass</code> ) 选中了 4 个元素，然后这四个元素的索引值会被分配为 <code>0</code>到<code>3</code>，之后就可以用这种索引值选择器来进一步筛选了。</p>
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<p>请注意，由于JavaScript数组使用<em>基于0的索引</em> ，这些选择器也是如此。这就是为什么<code>$('.myclass:lt(1)')</code>选择器选择文档中第一个<code>MyClass</code>类的元素，而不是选择不到任何元素。与此相反，<code>:nth-child(n)</code>是<em>基于1的索引</em>的，以符合CSS规范。</p>
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<p>
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jQuery 1.8以前的版本，<code>:lt(index)</code>选择器不接收一个负数的<code>index</code>值。</p>
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</div>
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<h3>Additional Notes（其他注意事项）:</h3>
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<div class="longdesc"><ul>
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<li>
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因为 <code>:lt()</code> 是一个 jQuery 延伸出来的一个选择器 ， 并且不是的CSS规范的一部分, 使用<code>:lt()</code>查询不能充分利用原生DOM提供的<code>querySelectorAll()</code> 方法来提高性能。为了在现代浏览器上获得更佳的性能，请使用<code>$("your-pure-css-selector").slice(0, index)</code>代替。
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</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">查找索引值小于 4 的 td.</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 n13">13</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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</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">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 class="attribute">border</span>=<span class="value">"1"</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>TD #0<span class="tag"></<span class="title">td</span>></span><span class="tag"><<span class="title">td</span>></span>TD #1<span class="tag"></<span class="title">td</span>></span><span class="tag"><<span class="title">td</span>></span>TD #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> <span class="tag"><<span class="title">tr</span>></span><span class="tag"><<span class="title">td</span>></span>TD #3<span class="tag"></<span class="title">td</span>></span><span class="tag"><<span class="title">td</span>></span>TD #4<span class="tag"></<span class="title">td</span>></span><span class="tag"><<span class="title">td</span>></span>TD #5<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>TD #6<span class="tag"></<span class="title">td</span>></span><span class="tag"><<span class="title">td</span>></span>TD #7<span class="tag"></<span class="title">td</span>></span><span class="tag"><<span class="title">td</span>></span>TD #8<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">"td:lt(4)"</span>).css(<span class="string">"color"</span>, <span class="string">"red"</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> |