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132 lines
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132 lines
12 KiB
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<article id="wikiArticle">
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<div></div>
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<h2 id="Summary" name="Summary">概述</h2>
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<p><code><strong>JSON.parse()</strong></code> 方法用来解析JSON字符串，构造由字符串描述的JavaScript值或对象。提供可选的reviver函数用以在返回之前对所得到的对象执行变换(操作)。</p>
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<div><iframe class="interactive interactive-js" frameborder="0" height="250" src="https://interactive-examples.mdn.mozilla.net/pages/js/json-parse.html" width="100%"></iframe></div>
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<p class="hidden">The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone <a class="external" href="https://github.com/mdn/interactive-examples" rel="noopener">https://github.com/mdn/interactive-examples</a> and send us a pull request.</p>
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<h2 id="Syntax" name="Syntax">语法</h2>
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<pre><code class="language-javascript">JSON.parse(<em>text</em>[, <em>reviver</em>])</code></pre>
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<h3 id="Parameters" name="Parameters">参数</h3>
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<dl>
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<dt><code>text</code></dt>
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<dd>要被解析成JavaScript值的字符串，关于JSON的语法格式,请参考: <a href="Reference/Global_Objects/JSON" title="JSON对象包含两个方法: 用于解析 JavaScript Object Notation (JSON) 的 parse() 方法，以及将对象/值转换为 JSON字符串的 stringify() 方法。除了这两个方法, JSON这个对象本身并没有其他作用，也不能被调用或者作为构造函数调用。"><code>JSON</code></a>。</dd>
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<dt><code>reviver</code> <span class="inlineIndicator optional optionalInline">可选</span></dt>
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<dd>转换器, 如果传入该参数(函数)，可以用来修改解析生成的原始值，调用时机在parse函数返回之前。</dd>
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</dl>
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<h3 id="Returns" name="Returns">返回值</h3>
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<p><a href="Reference/Global_Objects/Object" title="Object 构造函数创建一个对象包装器。"><code>Object</code></a>类型, 对应给定JSON文本的对象/值。</p>
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<h3 id="Throws" name="Throws">异常</h3>
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<p>若传入的字符串不符合 JSON 规范，则会抛出 <a href="Reference/Global_Objects/SyntaxError" title="SyntaxError 对象代表尝试解析语法上不合法的代码的错误。"><code>SyntaxError</code></a> 异常。</p>
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<h2 id="Examples" name="Examples">示例</h2>
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<h3 id="Example:_Using_JSON.parse" name="Example:_Using_JSON.parse">使用 <code>JSON.parse()</code></h3>
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<pre><code class="language-javascript">JSON.parse('{}'); // {}
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JSON.parse('true'); // true
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JSON.parse('"foo"'); // "foo"
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JSON.parse('[1, 5, "false"]'); // [1, 5, "false"]
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JSON.parse('null'); // null
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JSON.parse('1'); // 1
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</code></pre>
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<p> </p>
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<h3 id="Example:_Using_the_reviver_parameter" name="Example:_Using_the_reviver_parameter">使用 <code>reviver</code> 函数</h3>
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<p>如果指定了 <code>reviver</code> 函数，则解析出的 JavaScript 值（解析值）会经过一次转换后才将被最终返回（返回值）。更具体点讲就是：解析值本身以及它所包含的所有属性，会按照一定的顺序（从最最里层的属性开始，一级级往外，最终到达顶层，也就是解析值本身）分别的去调用 <code>reviver</code> 函数，在调用过程中，当前属性所属的对象会作为 <code>this</code> 值，当前属性名和属性值会分别作为第一个和第二个参数传入 <code>reviver</code> 中。如果 <code>reviver</code> 返回 <code>undefined</code>，则当前属性会从所属对象中删除，如果返回了其他值，则返回的值会成为当前属性新的属性值。</p>
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<p>当遍历到最顶层的值（解析值）时，传入 <code>reviver</code> 函数的参数会是空字符串 <code>""</code>（因为此时已经没有真正的属性）和当前的解析值（有可能已经被修改过了），当前的 <code>this</code> 值会是 <code>{"": 修改过的解析值}</code>，在编写 <code>reviver</code> 函数时，要注意到这个特例。（这个函数的遍历顺序依照：从最内层开始，按照层级顺序，依次向外遍历）</p>
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<pre><code class="language-javascript">JSON.parse('{"p": 5}', function (k, v) {
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if(k === '') return v; // 如果到了最顶层，则直接返回属性值，
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return v * 2; // 否则将属性值变为原来的 2 倍。
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}); // { p: 10 }
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JSON.parse('{"1": 1, "2": 2,"3": {"4": 4, "5": {"6": 6}}}', function (k, v) {
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console.log(k); // 输出当前的属性名，从而得知遍历顺序是从内向外的，
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// 最后一个属性名会是个空字符串。
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return v; // 返回原始属性值，相当于没有传递 reviver 参数。
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});
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// 1
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// 2
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// 4
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// 6
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// 5
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// 3
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// ""
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</code></pre>
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<h3 id="JSON.parse()_不允许用逗号作为结尾"><code>JSON.parse()</code> 不允许用逗号作为结尾</h3>
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<pre class="example-bad brush: js">// both will throw a SyntaxError
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JSON.parse("[1, 2, 3, 4, ]");
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JSON.parse('{"foo" : 1, }');
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</code></pre>
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<h2 id="Specifications" name="Specifications">规范</h2>
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<table class="standard-table">
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<tbody>
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<tr>
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<th scope="col">规范名称</th>
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<th scope="col">规范状态</th>
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<th scope="col">备注</th>
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</tr>
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<tr>
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<td><a class="external" href="https://www.ecma-international.org/ecma-262/5.1/#sec-15.12.2" hreflang="en" lang="en" rel="noopener">ECMAScript 5.1 (ECMA-262)<br/><small lang="zh-CN">JSON.parse</small></a></td>
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<td><span class="spec-Standard">Standard</span></td>
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<td>首次定义，于 JavaScript 1.7 版本中实现。</td>
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</tr>
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<tr>
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<td><a class="external" href="https://www.ecma-international.org/ecma-262/6.0/#sec-json.parse" hreflang="en" lang="en" rel="noopener">ECMAScript 2015 (6th Edition, ECMA-262)<br/><small lang="zh-CN">JSON.parse</small></a></td>
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<td><span class="spec-Standard">Standard</span></td>
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<td> </td>
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</tr>
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</tbody>
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</table>
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<h2 id="Browser_compatibility" name="Browser_compatibility">浏览器兼容性</h2>
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<div>
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<div class="hidden">The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out <a class="external" href="https://github.com/mdn/browser-compat-data" rel="noopener">https://github.com/mdn/browser-compat-data</a> and send us a pull request.</div>
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<p></p><div class="bc-data"><a class="bc-github-link external" href="https://github.com/mdn/browser-compat-data" rel="noopener">Update compatibility data on GitHub</a><table class="bc-table bc-table-js"><thead><tr class="bc-platforms"><td></td><th class="bc-platform-desktop" colspan="6"><span>Desktop</span></th><th class="bc-platform-mobile" colspan="7"><span>Mobile</span></th><th class="bc-platform-server" colspan="1"><span>Server</span></th></tr><tr class="bc-browsers"><td></td><th class="bc-browser-chrome"><span class="bc-head-txt-label bc-head-icon-chrome">Chrome</span></th><th class="bc-browser-edge"><span class="bc-head-txt-label bc-head-icon-edge">Edge</span></th><th class="bc-browser-firefox"><span class="bc-head-txt-label bc-head-icon-firefox">Firefox</span></th><th class="bc-browser-ie"><span class="bc-head-txt-label bc-head-icon-ie">Internet Explorer</span></th><th class="bc-browser-opera"><span class="bc-head-txt-label bc-head-icon-opera">Opera</span></th><th class="bc-browser-safari"><span class="bc-head-txt-label bc-head-icon-safari">Safari</span></th><th class="bc-browser-webview_android"><span class="bc-head-txt-label bc-head-icon-webview_android">Android webview</span></th><th class="bc-browser-chrome_android"><span class="bc-head-txt-label bc-head-icon-chrome_android">Chrome for Android</span></th><th class="bc-browser-edge_mobile"><span class="bc-head-txt-label bc-head-icon-edge_mobile">Edge Mobile</span></th><th class="bc-browser-firefox_android"><span class="bc-head-txt-label bc-head-icon-firefox_android">Firefox for Android</span></th><th class="bc-browser-opera_android"><span class="bc-head-txt-label bc-head-icon-opera_android">Opera for Android</span></th><th class="bc-browser-safari_ios"><span class="bc-head-txt-label bc-head-icon-safari_ios">Safari on iOS</span></th><th class="bc-browser-samsunginternet_android"><span class="bc-head-txt-label bc-head-icon-samsunginternet_android">Samsung Internet</span></th><th class="bc-browser-nodejs"><span class="bc-head-txt-label bc-head-icon-nodejs">Node.js</span></th></tr></thead><tbody><tr><th scope="row"><code>parse</code></th><td class="bc-supports-yes bc-browser-chrome"><span class="bc-browser-name">Chrome</span><abbr class="bc-level-yes only-icon" title="Full support">
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<span>Full support</span>
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</abbr>
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Yes</td><td class="bc-supports-yes bc-browser-edge"><span class="bc-browser-name">Edge</span><abbr class="bc-level-yes only-icon" title="Full support">
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<span>Full support</span>
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</abbr>
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12</td><td class="bc-supports-yes bc-browser-firefox"><span class="bc-browser-name">Firefox</span><abbr class="bc-level-yes only-icon" title="Full support">
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<span>Full support</span>
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</abbr>
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3.5</td><td class="bc-supports-yes bc-browser-ie"><span class="bc-browser-name">IE</span><abbr class="bc-level-yes only-icon" title="Full support">
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<span>Full support</span>
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</abbr>
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8</td><td class="bc-supports-yes bc-browser-opera"><span class="bc-browser-name">Opera</span><abbr class="bc-level-yes only-icon" title="Full support">
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<span>Full support</span>
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</abbr>
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10.5</td><td class="bc-supports-yes bc-browser-safari"><span class="bc-browser-name">Safari</span><abbr class="bc-level-yes only-icon" title="Full support">
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<span>Full support</span>
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</abbr>
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4</td><td class="bc-supports-yes bc-browser-webview_android"><span class="bc-browser-name">WebView Android</span><abbr class="bc-level-yes only-icon" title="Full support">
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<span>Full support</span>
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</abbr>
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Yes</td><td class="bc-supports-yes bc-browser-chrome_android"><span class="bc-browser-name">Chrome Android</span><abbr class="bc-level-yes only-icon" title="Full support">
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<span>Full support</span>
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</abbr>
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Yes</td><td class="bc-supports-yes bc-browser-edge_mobile"><span class="bc-browser-name">Edge Mobile</span><abbr class="bc-level-yes only-icon" title="Full support">
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<span>Full support</span>
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</abbr>
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Yes</td><td class="bc-supports-yes bc-browser-firefox_android"><span class="bc-browser-name">Firefox Android</span><abbr class="bc-level-yes only-icon" title="Full support">
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<span>Full support</span>
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</abbr>
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4</td><td class="bc-supports-yes bc-browser-opera_android"><span class="bc-browser-name">Opera Android</span><abbr class="bc-level-yes only-icon" title="Full support">
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<span>Full support</span>
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</abbr>
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Yes</td><td class="bc-supports-yes bc-browser-safari_ios"><span class="bc-browser-name">Safari iOS</span><abbr class="bc-level-yes only-icon" title="Full support">
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<span>Full support</span>
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</abbr>
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Yes</td><td class="bc-supports-yes bc-browser-samsunginternet_android"><span class="bc-browser-name">Samsung Internet Android</span><abbr class="bc-level-yes only-icon" title="Full support">
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<span>Full support</span>
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</abbr>
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Yes</td><td class="bc-supports-yes bc-browser-nodejs"><span class="bc-browser-name">nodejs</span><abbr class="bc-level-yes only-icon" title="Full support">
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<span>Full support</span>
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</abbr>
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Yes</td></tr></tbody></table><section class="bc-legend" id="sect1"><h3 class="offscreen" id="Legend">Legend</h3><dl><dt><span class="bc-supports-yes bc-supports">
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<abbr class="bc-level bc-level-yes only-icon" title="Full support">
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<span>Full support</span>
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</abbr></span></dt><dd>Full support</dd></dl></section></div><p></p>
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</div>
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<h2 id="See_also" name="See_also">相关链接</h2>
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<ul>
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<li><a href="Reference/Global_Objects/JSON/stringify" title="JSON.stringify() 方法是将一个JavaScript值(对象或者数组)转换为一个 JSON字符串，如果指定了replacer是一个函数，则可以替换值，或者如果指定了replacer是一个数组，可选的仅包括指定的属性。"><code>JSON.stringify()</code></a></li>
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</ul>
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</article> |