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243 lines
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243 lines
18 KiB
HTML
<article class="" id="post-">
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<header class="entry-header">
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<h1 class="entry-title">jQuery.getJSON()</h1>
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<div class="entry-meta">
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所属分类：<span class="category"><a href="/category/ajax/">Ajax</a> > <a href="/category/ajax/shorthand-methods/">快捷方法</a></span>
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<span class="pull-right">英文文档：<a href="https://api.jquery123.com/jQuery.getJSON/" target="_blank">jQuery.getJSON()</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="jQuery-getJSON1"><h2 class="section-title">
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<span class="name">jQuery.getJSON( url [, data ] [, success(data, textStatus, jqXHR) ] )</span><span class="returns">返回: <a href="/Types/#jqXHR">jqXHR</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>使用一个HTTP GET请求从服务器加载JSON编码的数据。</p>
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<ul class="signatures"><li class="signature" id="jQuery-getJSON-url-data-successdata--textStatus--jqXHR">
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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.getJSON( url [, data ] [, success(data, textStatus, jqXHR) ] )</h4>
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<ul>
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<li>
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<div><strong>url</strong></div>
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<div>类型: <a href="/Types/#String">String</a>
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</div>
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<div>一个包含发送请求的URL字符串</div>
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</li>
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<li>
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<div><strong>data</strong></div>
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<div>类型: <a href="/Types/#PlainObject">PlainObject</a>
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</div>
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<div>发送给服务器的字符串或Key/value键值对。</div>
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</li>
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<li>
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<div><strong>success(data, textStatus, jqXHR)</strong></div>
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<div>类型: <a href="/Types/#Function">Function</a>()</div>
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<div>当请求成功后执行的回调函数。</div>
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</li>
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</ul>
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</li></ul>
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<div class="longdesc" id="entry-longdesc">
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<p>这是一个Ajax函数的缩写，这相当于:</p>
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<pre><div class="container"><div class="line"><code>$.ajax({</code></div></div><div class="container"><div class="line"><code> dataType: <span class="string">"json"</span>,</code></div></div><div class="container"><div class="line"><code> url: url,</code></div></div><div class="container"><div class="line"><code> data: data,</code></div></div><div class="container"><div class="line"><code> success: success</code></div></div><div class="container"><div class="line"><code>});</code></div></div></pre>
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<p>数据会被附加到一个查询字符串的URL中，发送到服务器。如果该值的<code>data</code>参数是一个普通的对象，它会转换为一个字符串并使用URL编码，然后才追加到URL中。</p>
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<p>大多数情况下都会指定一个请求成功后的回调函数：</p>
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<pre><div class="container"><div class="line"><code>$.getJSON(<span class="string">'ajax/test.json'</span>, <span class="keyword">function</span>(data) {</code></div></div><div class="container"><div class="line"><code> <span class="keyword">var</span> items = [];</code></div></div><div class="container"><div class="line"><code> </code></div></div><div class="container"><div class="line"><code> $.each(data, <span class="keyword">function</span>(key, val) {</code></div></div><div class="container"><div class="line"><code> items.push(<span class="string">'<li id="'</span> + key + <span class="string">'">'</span> + val + <span class="string">'</li>'</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> $(<span class="string">'<ul/>'</span>, {</code></div></div><div class="container"><div class="line"><code> <span class="string">'class'</span>: <span class="string">'my-new-list'</span>,</code></div></div><div class="container"><div class="line"><code> html: items.join(<span class="string">''</span>)</code></div></div><div class="container"><div class="line"><code> }).appendTo(<span class="string">'body'</span>);</code></div></div><div class="container"><div class="line"><code>});</code></div></div></pre>
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</div>
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<p>这个例子，当然遵循JSON文件的结构：</p>
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<pre><div class="container"><div class="line"><code>{</code></div></div><div class="container"><div class="line"><code> <span class="string">"one"</span>: <span class="string">"Singular sensation"</span>,</code></div></div><div class="container"><div class="line"><code> <span class="string">"two"</span>: <span class="string">"Beady little eyes"</span>,</code></div></div><div class="container"><div class="line"><code> <span class="string">"three"</span>: <span class="string">"Little birds pitch by my doorstep"</span></code></div></div><div class="container"><div class="line"><code>}</code></div></div></pre>
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<p>使用这种结构，这个例子遍历请求的数据，建立了一个无序列表，并追加到body。</p>
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<p>在<code>success</code>回调中传入返回的数据，通常是一个JavaScript对象或数组所定义的JSON结构，使用<a href="/jQuery.parseJSON"><code>$.parseJSON()</code></a>方法解析。它（<code>success</code>回调）也传入了响应状态文本。</p>
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<p><strong>在jQuery 1.5，</strong>，在<code>success</code>回调函数接收一个<a href="/jQuery.get/#jqxhr-object">“jqXHR”对象</a> （ 在<strong>jQuery 1.4</strong>中 ，它收到的是<code>XMLHttpRequest</code>对象）。然而，由于JSONP形式和跨域的GET请求不使用<abbr title="XmlHttpRequest">XHR</abbr>，在这些情况下， <code>jqXHR</code>和<code>textStatus</code>参数传递给success（成功）回调是 undefined 。</p>
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<blockquote>
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<p><strong>重要提示：</strong> 从jQuery 1.4开始，如果JSON文件包含一个语法错误，该请求通常会静静的失败。因此应该避免频繁手工编辑JSON数据。JSON语法规则比JavaScript对象字面量表示法更加严格。例如，所有在JSON中的字符串，无论是属性或值，必须用双引号括起来，更多JSON细节信息请参阅<a href="http://json.org/">http://json.org/</a> 。</p>
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</blockquote>
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<h4 id="jsonp">JSONP</h4>
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<p>如果URL包含字符串“callback=?”（或类似的参数，取决于服务器端 API 是如何定义的），这个请求被视为JSONP形式请求。更多<code>jsonp</code>数据类型的细节讨论，请参阅<a href="/jQuery.ajax/"><code>$.ajax()</code></a>。</p>
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<h4 id="jqxhr-object">The jqXHR Object（jqXHR 对象）</h4>
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<p>注：估计是jQuery官方没有及时的更新这条api，和<a href="/jQuery.get/#jqxhr-object">jQuery.get() api中的jqXHR 对象</a>描述上有差别。</p>
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<p><strong>从jQuery 1.5开始</strong>，所有jQuery的Ajax方法都返回一个<code>XMLHTTPRequest</code>对象的超集。这个通过<code>$.get()</code>方法返回的jQuery XHR对象，或“jqXHR，”实现了 Promise 接口，使它拥有 Promise 的所有属性，方法和行为（见<a href="/category/deferred-object/">Deferred object</a>获取更多信息）。
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为了便于在 <code>$.ajax()</code>里使用，jQuery XHR 对象<a href="/jQuery.ajax"><code>$.ajax()</code></a>同样也提供了<code>.error()</code> <code>.success()</code>和<code>.complete()</code>方法。这些方法接受一个函数参数，用来请求终止时被调用。这个函数接收与<code>$.ajax()</code>回调函数名中相同的参数。</p>
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<p>Promise 接口也允许jQuery的Ajax方法, 包括 <code>$.getJSON()</code>, 在一个单独的请求中关联到 <code>.success()</code>, <code>.complete()</code>, 和 <code>.error()</code> 回调函数， 甚至允许你在请求已经结束后，指派回调函数。如果该请求已经完成，则回调函数会被立刻调用。</p>
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<pre><div class="container"><div class="line"><code><span class="comment">// Assign handlers immediately after making the request,</span></code></div></div><div class="container"><div class="line"><code><span class="comment">// and remember the jqxhr object for this request</span></code></div></div><div class="container"><div class="line"><code><span class="keyword">var</span> jqxhr = $.getJSON(<span class="string">"example.json"</span>, <span class="keyword">function</span>() {</code></div></div><div class="container"><div class="line"><code> alert(<span class="string">"success"</span>);</code></div></div><div class="container"><div class="line"><code>})</code></div></div><div class="container"><div class="line"><code>.success(<span class="keyword">function</span>() { alert(<span class="string">"second success"</span>); })</code></div></div><div class="container"><div class="line"><code>.error(<span class="keyword">function</span>() { alert(<span class="string">"error"</span>); })</code></div></div><div class="container"><div class="line"><code>.complete(<span class="keyword">function</span>() { alert(<span class="string">"complete"</span>); });</code></div></div><div class="container"><div class="line"><code> </code></div></div><div class="container"><div class="line"><code><span class="comment">// perform other work here ...</span></code></div></div><div class="container"><div class="line"><code> </code></div></div><div class="container"><div class="line"><code><span class="comment">// Set another completion function for the request above</span></code></div></div><div class="container"><div class="line"><code>jqxhr.complete(<span class="keyword">function</span>(){ alert(<span class="string">"second complete"</span>); });</code></div></div></pre>
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<h4>Deprecation Notice(弃用通知)</h4>
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<p>jQuery 1.5中引进的
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<code>jqXHR.success()</code>,<code>jqXHR.error()</code>,<code>jqXHR.complete()</code>回调方法在<strong>jQuery 1.8中废弃</strong>。你的代码因做好准备，他们最终将被移除，使用<code>jqXHR.done()</code>, <code>jqXHR.fail()</code>, 和 <code>jqXHR.always()</code>代替。</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">
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<ul>
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<li> 由于浏览器的安全限制，大多数“Ajax”的要求，均采用<a href="http://en.wikipedia.org/wiki/Same_origin_policy" title="维基百科上的同源策略">同一起源的政策</a> ;即无法从不同的域，子域或协议中正确接收数据。</li>
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<li>Script和JSONP形式请求不受同源策略的限制。</li>
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</ul>
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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">从 Flickr JSONP API中加载最近的四张标签为猫的图片：</span>
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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">img</span><span class="rules">{ <span class="rule"><span class="attribute">height</span>:<span class="value"> <span class="number">100</span>px;</span></span> <span class="rule"><span class="attribute">float</span>:<span class="value"> left;</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">div</span> <span class="attribute">id</span>=<span class="value">"images"</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">script</span>></span><span class="javascript"></span></code></div></div><div class="container"><div class="line"><code>$.getJSON(<span class="string">"http://api.flickr.com/services/feeds/photos_public.gne?jsoncallback=?"</span>,</code></div></div><div class="container"><div class="line"><code> {</code></div></div><div class="container"><div class="line"><code> tags: <span class="string">"mount rainier"</span>,</code></div></div><div class="container"><div class="line"><code> tagmode: <span class="string">"any"</span>,</code></div></div><div class="container"><div class="line"><code> format: <span class="string">"json"</span></code></div></div><div class="container"><div class="line"><code> },</code></div></div><div class="container"><div class="line"><code> <span class="keyword">function</span>(data) {</code></div></div><div class="container"><div class="line"><code> $.each(data.items, <span class="keyword">function</span>(i,item){</code></div></div><div class="container"><div class="line"><code> $(<span class="string">"<img/>"</span>).attr(<span class="string">"src"</span>, item.media.m).appendTo(<span class="string">"#images"</span>);</code></div></div><div class="container"><div class="line"><code> <span class="keyword">if</span> ( i == <span class="number">3</span> ) <span class="keyword">return</span> <span class="literal">false</span>;</code></div></div><div class="container"><div class="line"><code> });</code></div></div><div class="container"><div class="line"><code> });<span class="tag"></<span class="title">script</span>></span></code></div></div><div class="container"><div class="line"><code> </code></div></div><div class="container"><div class="line"><code><span class="tag"></<span class="title">body</span>></span></code></div></div><div class="container"><div class="line"><code><span class="tag"></<span class="title">html</span>></span></code></div></div></pre>
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<h4>Demo:</h4>
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<div class="demo code-demo"></div>
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<div class="entry-example" id="example-1">
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<h4>Example: <span class="desc"> 通过test.js加载这个JSON数据，并使用返回的JSON数据中的 name值：</span>
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<pre><div class="container"><div class="line"><code>$.getJSON(<span class="string">"test.js"</span>, <span class="keyword">function</span>(json) {</code></div></div><div class="container"><div class="line"><code> alert(<span class="string">"JSON Data: "</span> + json.users[<span class="number">3</span>].name);</code></div></div><div class="container"><div class="line"><code> });</code></div></div></pre>
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<div class="entry-example" id="example-2">
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<h4>Example: <span class="desc">通过额外的Key/value参数从test.js加载这个JSON数据,并使用返回的JSON数据中的 name值：.</span>
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<pre><div class="container"><div class="line"><code>$.getJSON(<span class="string">"test.js"</span>, { name: <span class="string">"John"</span>, time: <span class="string">"2pm"</span> }, <span class="keyword">function</span>(json) {</code></div></div><div class="container"><div class="line"><code> alert(<span class="string">"JSON Data: "</span> + json.users[<span class="number">3</span>].name);</code></div></div><div class="container"><div class="line"><code> });</code></div></div></pre>
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