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197 lines
21 KiB
HTML
197 lines
21 KiB
HTML
<article class="" id="post-">
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<header class="entry-header">
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<h1 class="entry-title">.end()</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/miscellaneous-traversal/">其它遍历</a></span>
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<span class="pull-right">英文文档：<a href="https://api.jquery123.com/end/" target="_blank">.end()</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="end1"><h2 class="section-title">
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<span class="name">.end()</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>
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终止在当前链的最新过滤操作，并返回匹配的元素的以前状态。</p>
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<ul class="signatures"><li class="signature" id="end">
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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>.end()</h4>
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<ul><li><div class="null-signature">这个方法不接受任何参数。</div></li></ul>
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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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大多数 jQuery<a href="/category/traversing">DOM遍历</a> 方法来操作 jQuery 对象实例，并创建一个新的对象，匹配一个不同的 DOM 元素集合。当发生这种情况时，实际上是新的元素集合被压入到对象内部维护的栈中。每次过滤方法都会被压入栈中。当我们需要返回到前一个状态时，我们可以使用<code>end()</code> 进行出栈操作，来返回栈中的前一个状态。
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</p>
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<p>假设页面上有几个短的列表</p>
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<pre><div class="container"><div class="line"><code><span class="tag"><<span class="title">ul</span> <span class="attribute">class</span>=<span class="value">"first"</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">"foo"</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">"bar"</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">ul</span>></span></code></div></div><div class="container"><div class="line"><code><span class="tag"><<span class="title">ul</span> <span class="attribute">class</span>=<span class="value">"second"</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">"foo"</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">"bar"</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">ul</span>></span></code></div></div></pre>
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<p><code>end()</code> 方法主要用于 jQuery 的链式属性中。当没有使用链式用法时，我们通常只是调用变量名上的前一个对象，所以我们不需要操作栈。使用 <code>end()</code> 时，我们可以一次性调用所有需要的方法：
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</p>
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<div class="syntaxhighlighter javascript nogutter">
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<table>
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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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<td class="code">
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<pre><div class="container"><div class="line"><code>$(<span class="string">'ul.first'</span>).find(<span class="string">'.foo'</span>).css(<span class="string">'background-color'</span>, <span class="string">'red'</span>)</code></div></div><div class="container"><div class="line"><code> .end().find(<span class="string">'.bar'</span>).css(<span class="string">'background-color'</span>, <span class="string">'green'</span>);</code></div></div></pre>
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<p>在上面的代码中，首先在链式用法中只在第一个列表中查找样式为 <code>foo</code> 的项目，并将其背景色变成红色。然后 <code>end()</code> 返回调用 <code>find()</code> 之前的状态。因此，第二次 <code>find()</code> 将只会查找 <code><ul class="first"></code> 中的 '.bar'，而不是继续在 <code><li class="foo"></code> 中进行查找，结果是将匹配到的元素的背景色变成绿色。上述代码的最终结果是，第一个列表中的第 1 和第 3 个列表项的背景色有颜色，而第二个列表中的任何项目都没有背景色。
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</p>
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<p>对于一个长的 jQuery 链式写法，可以使用结构块的写法，让其具有很好的可读性，即：将 <code>end()</code> 方法与其对应的过滤方法写在一个嵌套块中，例如：
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</p>
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<div class="syntaxhighlighter javascript nogutter">
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<table>
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<tbody>
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<tr>
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<td class="gutter">
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<div class="line n1">1</div>
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<div class="line n2">2</div>
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<div class="line n3">3</div>
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<td class="code">
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<pre><div class="container"><div class="line"><code>$(<span class="string">'ul.first'</span>).find(<span class="string">'.foo'</span>)</code></div></div><div class="container"><div class="line"><code> .css(<span class="string">'background-color'</span>, <span class="string">'red'</span>)</code></div></div><div class="container"><div class="line"><code>.end().find(<span class="string">'.bar'</span>)</code></div></div><div class="container"><div class="line"><code> .css(<span class="string">'background-color'</span>, <span class="string">'green'</span>)</code></div></div><div class="container"><div class="line"><code>.end();</code></div></div></pre>
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</td>
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<p>最后的<code>end()</code>是不必要的，我们丢弃紧随其后的jQuery对象。然而，当编写这种形式的代码，<code>end()</code>提供了可视化的对称性和完整性，至少一些开发者的眼中，更具可读性，这样存在一些性能成本，因为它是一个额外的函数调用。</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">选择所有的段落，在其中查找 span 元素，之后再恢复到选择段落的状态。</span>
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</h4>
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<div class="syntaxhighlighter xml ">
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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">p</span>, <span class="tag">div</span> <span class="rules">{ <span class="rule"><span class="attribute">margin</span>:<span class="value"><span class="number">1</span>px;</span></span> <span class="rule"><span class="attribute">padding</span>:<span class="value"><span class="number">1</span>px;</span></span> <span class="rule"><span class="attribute">font-weight</span>:<span class="value">bold;</span></span></span></code></div></div><div class="container"><div class="line"><code> <span class="rule"><span class="attribute">font-size</span>:<span class="value"><span class="number">16</span>px;</span></span> <span class="rule">}</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">color</span>:<span class="value">blue;</span></span> <span class="rule">}</span></span></code></div></div><div class="container"><div class="line"><code> <span class="tag">b</span> <span class="rules">{ <span class="rule"><span class="attribute">color</span>:<span class="value">red;</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">p</span>></span></code></div></div><div class="container"><div class="line"><code> Hi there <span class="tag"><<span class="title">span</span>></span>how<span class="tag"></<span class="title">span</span>></span> are you <span class="tag"><<span class="title">span</span>></span>doing<span class="tag"></<span class="title">span</span>></span>?</code></div></div><div class="container"><div class="line"><code> <span class="tag"></<span class="title">p</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></code></div></div><div class="container"><div class="line"><code> This <span class="tag"><<span class="title">span</span>></span>span<span class="tag"></<span class="title">span</span>></span> is one of</code></div></div><div class="container"><div class="line"><code> several <span class="tag"><<span class="title">span</span>></span>spans<span class="tag"></<span class="title">span</span>></span> in this</code></div></div><div class="container"><div class="line"><code> <span class="tag"><<span class="title">span</span>></span>sentence<span class="tag"></<span class="title">span</span>></span>.</code></div></div><div class="container"><div class="line"><code> <span class="tag"></<span class="title">p</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></code></div></div><div class="container"><div class="line"><code> Tags in jQuery object initially: <span class="tag"><<span class="title">b</span>></span><span class="tag"></<span class="title">b</span>></span></code></div></div><div class="container"><div class="line"><code> <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></code></div></div><div class="container"><div class="line"><code> Tags in jQuery object after find: <span class="tag"><<span class="title">b</span>></span><span class="tag"></<span class="title">b</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></code></div></div><div class="container"><div class="line"><code> <span class="tag"><<span class="title">div</span>></span></code></div></div><div class="container"><div class="line"><code> Tags in jQuery object after end: <span class="tag"><<span class="title">b</span>></span><span class="tag"></<span class="title">b</span>></span></code></div></div><div class="container"><div class="line"><code> <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">script</span>></span><span class="javascript"></span></code></div></div><div class="container"><div class="line"><code>jQuery.fn.showTags = <span class="function"><span class="keyword">function</span> <span class="params">(n)</span> {</span></code></div></div><div class="container"><div class="line"><code> <span class="keyword">var</span> tags = <span class="keyword">this</span>.map(<span class="function"><span class="keyword">function</span> <span class="params">()</span> {</span></code></div></div><div class="container"><div class="line"><code> <span class="keyword">return</span> <span class="keyword">this</span>.tagName;</code></div></div><div class="container"><div class="line"><code> })</code></div></div><div class="container"><div class="line"><code> .get().join(<span class="string">", "</span>);</code></div></div><div class="container"><div class="line"><code> $(<span class="string">"b:eq("</span> + n + <span class="string">")"</span>).text(tags);</code></div></div><div class="container"><div class="line"><code> <span class="keyword">return</span> <span class="keyword">this</span>;</code></div></div><div class="container"><div class="line"><code>};</code></div></div><div class="container"><div class="line"><code> </code></div></div><div class="container"><div class="line"><code>$(<span class="string">"p"</span>).showTags(<span class="number">0</span>)</code></div></div><div class="container"><div class="line"><code> .find(<span class="string">"span"</span>)</code></div></div><div class="container"><div class="line"><code> .showTags(<span class="number">1</span>)</code></div></div><div class="container"><div class="line"><code> .css(<span class="string">"background"</span>, <span class="string">"yellow"</span>)</code></div></div><div class="container"><div class="line"><code> .end()</code></div></div><div class="container"><div class="line"><code> .showTags(<span class="number">2</span>)</code></div></div><div class="container"><div class="line"><code> .css(<span class="string">"font-style"</span>, <span class="string">"italic"</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">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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</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">Selects all paragraphs, finds span elements inside these, and reverts the selection back to the paragraphs.</span>
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</h4>
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<div class="syntaxhighlighter xml ">
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<table>
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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 class="tag">p</span> <span class="rules">{ <span class="rule"><span class="attribute">margin</span>:<span class="value"><span class="number">10</span>px;</span></span> <span class="rule"><span class="attribute">padding</span>:<span class="value"><span class="number">10</span>px;</span></span> <span class="rule">}</span></span></span><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">p</span>></span><span class="tag"><<span class="title">span</span>></span>Hello<span class="tag"></<span class="title">span</span>></span>, how are you?<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>).find(<span class="string">"span"</span>).end().css(<span class="string">"border"</span>, <span class="string">"2px red solid"</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>
|
||
<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> |