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159 lines
16 KiB
HTML
159 lines
16 KiB
HTML
<article class="" id="post-">
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<header class="entry-header">
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<h1 class="entry-title">.prev()</h1>
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<div class="entry-meta">
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所属分类：<span class="category"><a href="/category/traversing/">遍历</a> > <a href="/category/traversing/tree-traversal/">树遍历</a></span>
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<span class="pull-right">英文文档：<a href="https://api.jquery123.com/prev/" target="_blank">.prev()</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 method" id="prev1"><h2 class="section-title">
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<span class="name">.prev( [selector ] )</span><span class="returns">返回: <a href="/Types/#jQuery">jQuery</a></span>
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</h2>
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<div class="entry-wrapper">
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<p class="desc"><strong>描述: </strong>取得一个包含匹配的元素集合中每一个元素紧邻的前一个同辈元素的元素集合。选择性筛选的选择器。</p>
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<ul class="signatures"><li class="signature" id="prev-selector">
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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>.prev( [selector ] )</h4>
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<ul><li>
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<div><strong>selector</strong></div>
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<div>类型: <a href="/Types/#Selector">Selector</a>
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</div>
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<div>一个用于匹配元素的选择器字符串。</div>
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</li></ul>
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</li></ul>
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<div class="longdesc" id="entry-longdesc">
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<p>如果提供的jQuery代表了一组DOM元素，<code>.prev()</code>方法通过这些元素组合传递到方法构造一个新的jQuery对象。</p>
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<p>该方法选择性地接受同一类型选择器表达式，我们可以传递给<code>$()</code>函数。如果选择供应，将被过滤的元素通过测试它们是否匹配。</p>
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<p>考虑一个页上有一个简单的列表：</p>
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<div class="syntaxhighlighter xml nogutter">
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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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</td>
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<td class="code">
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<pre><div class="container"><div class="line"><code><span class="tag"><<span class="title">ul</span>></span></code></div></div><div class="container"><div class="line"><code> <span class="tag"><<span class="title">li</span>></span>list item 1<span class="tag"></<span class="title">li</span>></span></code></div></div><div class="container"><div class="line"><code> <span class="tag"><<span class="title">li</span>></span>list item 2<span class="tag"></<span class="title">li</span>></span></code></div></div><div class="container"><div class="line"><code> <span class="tag"><<span class="title">li</span> <span class="attribute">class</span>=<span class="value">"third-item"</span>></span>list item 3<span class="tag"></<span class="title">li</span>></span></code></div></div><div class="container"><div class="line"><code> <span class="tag"><<span class="title">li</span>></span>list item 4<span class="tag"></<span class="title">li</span>></span></code></div></div><div class="container"><div class="line"><code> <span class="tag"><<span class="title">li</span>></span>list item 5<span class="tag"></<span class="title">li</span>></span></code></div></div><div class="container"><div class="line"><code><span class="tag"></<span class="title">ul</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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<p>如果我们开始在第三个项目，我们可以找到元素的紧邻的前一个同辈元素：</p>
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<div class="syntaxhighlighter javascript nogutter">
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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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</td>
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<td class="code">
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<pre><div class="container"><div class="line"><code>$(<span class="string">'li.third-item'</span>).prev().css(<span class="string">'background-color'</span>, <span class="string">'red'</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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<p>此调用的结果是项目2红色背景。由于我们没有提供一个选择的表达，所有的兄弟姐妹都是对象的一部分。如果我们提供的一个，其中只有四个匹配的项目将包括在内。</p>
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<p>如果上一个兄弟不存在，或如果前面的同级元素不匹配所提供的选择器，返回一个空的jQuery对象。</p>
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<p>要选择前面<em>所有</em>的同辈元素，而不仅仅是一个相邻的兄弟，请使用<a href="/prevAll">.prevAll()</a>方法。</p>
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</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>Example: <span class="desc">Find the very previous sibling of each div.</span>
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</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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<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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<div class="line n21">21</div>
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<div class="line n22">22</div>
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<div class="line n23">23</div>
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<div class="line n24">24</div>
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<div class="line n25">25</div>
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<div class="line n26">26</div>
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<div class="line n27">27</div>
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<div class="line n28">28</div>
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<div class="line n29">29</div>
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<div class="line n30">30</div>
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<div class="line n31">31</div>
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<div class="line n32">32</div>
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<div class="line n33">33</div>
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<div class="line n34">34</div>
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<div class="line n35">35</div>
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<div class="line n36">36</div>
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<div class="line n37">37</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> <span class="tag">div</span> <span class="rules">{ <span class="rule"><span class="attribute">width</span>:<span class="value"><span class="number">40</span>px;</span></span> <span class="rule"><span class="attribute">height</span>:<span class="value"><span class="number">40</span>px;</span></span> <span class="rule"><span class="attribute">margin</span>:<span class="value"><span class="number">10</span>px;</span></span></span></code></div></div><div class="container"><div class="line"><code> <span class="rule"><span class="attribute">float</span>:<span class="value">left;</span></span> <span class="rule"><span class="attribute">border</span>:<span class="value"><span class="number">2</span>px blue solid;</span></span> </code></div></div><div class="container"><div class="line"><code> <span class="rule"><span class="attribute">padding</span>:<span class="value"><span class="number">2</span>px;</span></span> <span class="rule">}</span></code></div></div><div class="container"><div class="line"><code> <span class="tag">span</span> <span class="rules">{ <span class="rule"><span class="attribute">font-size</span>:<span class="value"><span class="number">14</span>px;</span></span> <span class="rule">}</span></span></code></div></div><div class="container"><div class="line"><code> <span class="tag">p</span> <span class="rules">{ <span class="rule"><span class="attribute">clear</span>:<span class="value">left;</span></span> <span class="rule"><span class="attribute">margin</span>:<span class="value"><span class="number">10</span>px;</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">div</span>></span><span class="tag"></<span class="title">div</span>></span></code></div></div><div class="container"><div class="line"><code> <span class="tag"><<span class="title">div</span>></span><span class="tag"></<span class="title">div</span>></span></code></div></div><div class="container"><div class="line"><code> <span class="tag"><<span class="title">div</span>></span><span class="tag"><<span class="title">span</span>></span>has child<span class="tag"></<span class="title">span</span>></span><span class="tag"></<span class="title">div</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">div</span>></span><span class="tag"></<span class="title">div</span>></span></code></div></div><div class="container"><div class="line"><code> <span class="tag"><<span class="title">div</span>></span><span class="tag"></<span class="title">div</span>></span></code></div></div><div class="container"><div class="line"><code> <span class="tag"><<span class="title">div</span>></span><span class="tag"></<span class="title">div</span>></span></code></div></div><div class="container"><div class="line"><code> <span class="tag"><<span class="title">div</span> <span class="attribute">id</span>=<span class="value">"start"</span>></span><span class="tag"></<span class="title">div</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">div</span>></span><span class="tag"></<span class="title">div</span>></span></code></div></div><div class="container"><div class="line"><code> <span class="tag"><<span class="title">p</span>></span><span class="tag"><<span class="title">button</span>></span>Go to Prev<span class="tag"></<span class="title">button</span>></span><span class="tag"></<span class="title">p</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></code></div></div><div class="container"><div class="line"><code> <span class="keyword">var</span> $curr = $(<span class="string">"#start"</span>);</code></div></div><div class="container"><div class="line"><code> $curr.css(<span class="string">"background"</span>, <span class="string">"#f99"</span>);</code></div></div><div class="container"><div class="line"><code> $(<span class="string">"button"</span>).click(<span class="function"><span class="keyword">function</span> <span class="params">()</span> {</span></code></div></div><div class="container"><div class="line"><code> $curr = $curr.prev();</code></div></div><div class="container"><div class="line"><code> $(<span class="string">"div"</span>).css(<span class="string">"background"</span>, <span class="string">""</span>);</code></div></div><div class="container"><div class="line"><code> $curr.css(<span class="string">"background"</span>, <span class="string">"#f99"</span>);</code></div></div><div class="container"><div class="line"><code> });</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">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>
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<div class="entry-example" id="example-1">
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<h4>Example: <span class="desc">For each paragraph, find the very previous sibling that has a class "selected".</span>
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</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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</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">div</span>></span><span class="tag"><<span class="title">span</span>></span>Hello<span class="tag"></<span class="title">span</span>></span><span class="tag"></<span class="title">div</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">p</span> <span class="attribute">class</span>=<span class="value">"selected"</span>></span>Hello Again<span class="tag"></<span class="title">p</span>></span></code></div></div><div class="container"><div class="line"><code> <span class="tag"><<span class="title">p</span>></span>And Again<span class="tag"></<span class="title">p</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">"p"</span>).prev(<span class="string">".selected"</span>).css(<span class="string">"background"</span>, <span class="string">"yellow"</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"><iframe height="250" width="100%"></iframe></div>
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</div></section>
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</div></article> </div>
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</article> |