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133 lines
9.5 KiB
HTML
133 lines
9.5 KiB
HTML
<article class="" id="post-">
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<header class="entry-header">
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<h1 class="entry-title">.ready()</h1>
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<div class="entry-meta">
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所属分类:<span class="category"><a href="/category/events/">事件</a> > <a href="/category/events/document-loading/">文档加载</a></span>
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<span class="pull-right">英文文档:<a href="https://api.jquery123.com/ready/" target="_blank">.ready()</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="ready1"><h2 class="section-title">
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<span class="name">.ready( handler )</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>当DOM准备就绪时,指定一个函数来执行。</p>
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<ul class="signatures"><li class="signature" id="ready-handler">
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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>.ready( handler )</h4>
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<ul><li>
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<div><strong>handler</strong></div>
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<div>类型: <a href="/Types/#Function">Function</a>()</div>
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<div>当DOM准备就绪时,执行的一个函数。</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>虽然JavaScript提供了<code>load</code>事件,当页面执呈现时用来执行这个事件,直到所有的东西,如图像已被完全接收前,此事件不会被触发。在大多数情况下,只要DOM结构已完全加载时,脚本就可以运行。传递处理函数给<code>.ready()</code>方法,能保证DOM准备好后就执行这个函数,因此,这里是进行所有其它事件绑定及运行其它 jQuery 代码的最佳地方。当使用的脚本依赖 CSS 属性值时,需要特别注意,要保证外部的样式或内嵌的样式被加载完后,再调用脚本。</p>
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<p>如果执行的代码需要在元素被加载之后才能使用时,(例如,取得图片的大小需要在图片被加载完后才能知道),就需要将这样的代码放到 <code>load</code> 事件中。</p>
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<div class="warning"><p><code>.ready()</code>方法通常和<code><body onload=""></code>属性是不兼容的。如果<code>load</code>必须使用,要么不使用<code>.ready()</code>,要么使用jQuery的<code>.load()</code>方法向 window 或一些指定的元素(例如,图片)绑定 <code>load</code> 事件。</p>
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</div>
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<p>以下三个语法全部是等价的:</p>
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<ul>
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<li>
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<code>$(document).ready(handler)</code>
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</li>
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<li>
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<code>$().ready(handler)</code> (this is not recommended)</li>
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<li>
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<code>$(handler)</code>
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</li>
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</ul>
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<p>还有<code>$(document).bind("ready", handler)</code>。该方法在从 jQuery 1.8 开始不再建议使用。这种用法的行为和 ready 方法类似,只有一点不同:如果 .ready() 方法已经被执行,再试图进行 <code>.bind("ready")</code>的话,此时通过 <code>.bind("ready")</code> 绑定的函数是不会被立刻执行的,而是在使用上述三种方法之一进行绑定的函数执行完<em>后</em>,才会执行通过这种方法绑定的 ready 事件处理。(注:如果同时使用 .ready() 方法和 $(document).bind("ready", handler) 的话,那么始终会先执行 .ready(),再执行通过 bind 绑定的事件。)</p>
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<p><code>.ready()</code>方法方法只能被匹配当前文档的 jQuery 对象调用,因此选择符可能被省略。</p>
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<p><code>.ready()</code>方法通常用于一个匿名函数:</p>
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<div class="syntaxhighlighter javascript nogutter">
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<table>
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<tbody>
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<tr>
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<td class="gutter">
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<div class="line n1">1</div>
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<div class="line n2">2</div>
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<div class="line n3">3</div>
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</td>
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<td class="code">
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<pre><div class="container"><div class="line"><code>$(document).ready(<span class="keyword">function</span>() {</code></div></div><div class="container"><div class="line"><code> <span class="comment">// Handler for .ready() called.</span></code></div></div><div class="container"><div class="line"><code>});</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>这等价于调用:</p>
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<div class="syntaxhighlighter javascript nogutter">
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<table>
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<tbody>
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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>
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<td class="code">
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<pre><div class="container"><div class="line"><code>$(<span class="keyword">function</span>() {</code></div></div><div class="container"><div class="line"><code> <span class="comment">// Handler for .ready() called.</span></code></div></div><div class="container"><div class="line"><code> });</code></div></div></pre>
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</td>
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</tr>
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</tbody>
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</table>
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</div>
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<p>如果<code>.ready()</code>在DOM被初始化后被调用,新的处理函数通过将立即执行。</p>
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<h4>Aliasing the jQuery Namespace</h4>
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<p>当使用其他JavaScript库时,我们不妨调用<a href="/jQuery.noConflict"><code>$.noConflict()</code></a>以避免命名空间中的混淆。当这个函数被调用,<code>$</code>快捷方式将不再可用,迫使我们每次将写<code>$</code>的时候,写<code>jQuery</code>代替 。然而,处理函数传递给<code>.ready()</code>方法可以带一个参数,这个参数就是全局的<code>jQuery</code>对象。这意味着我们可以重新命名上下文对象内的<code>.ready()</code>处理函数,而不影响其他代码:</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>
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<td class="code">
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<pre><div class="container"><div class="line"><code>jQuery(document).ready(<span class="keyword">function</span>($) {</code></div></div><div class="container"><div class="line"><code> <span class="comment">// Code using $ as usual goes here.</span></code></div></div><div class="container"><div class="line"><code>});</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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</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">显示当DOM加载的信息。</span></h4>
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<div class="syntaxhighlighter xml ">
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<table>
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<tbody>
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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 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 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">style</span>></span><span class="css"><span class="tag">p</span> <span class="rules">{ <span class="rule"><span class="attribute">color</span>:<span class="value">red;</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">script</span>></span><span class="javascript"></span></code></div></div><div class="container"><div class="line"><code> $(document).ready(<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="string">"p"</span>).text(<span class="string">"The DOM is now loaded and can be manipulated."</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">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>Not loaded yet.<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">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> |