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112 lines
7.1 KiB
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112 lines
7.1 KiB
HTML
<article id="wikiArticle">
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<div> <div class="blockIndicator nonStandard nonStandardHeader">
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<p><strong><span class="icon-only-inline" title="This API has not been standardized."><i class="icon-warning-sign"> </i></span> 非标准</strong><br/>
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该特性是非标准的，请尽量不要在生产环境中使用它！</p>
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</div> <div class="blockIndicator deprecated deprecatedHeader">
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<p><strong><span class="icon-only-inline" title="This is an obsolete API and is no longer guaranteed to work."><i class="icon-trash"> </i></span> 已废弃</strong><br/>该特性已经从 Web 标准中删除，虽然一些浏览器目前仍然支持它，但也许会在未来的某个时间停止支持，请尽量不要使用该特性。</p>
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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>__lookupGetter__</strong></code> 方法会返回当前对象上指定属性的<strong>属性读取访问器函数（getter）。</strong></p>
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<h2 id="Syntax" name="Syntax">语法</h2>
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<pre><code class="language-javascript"><code><em>obj</em>.__lookupGetter__(<em>sprop</em>)</code></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>sprop</code></dt>
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<dd>属性名</dd>
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</dl>
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<h2 id="Examples" name="Examples">示例</h2>
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<pre><code class="language-javascript">var obj = {
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get foo() {
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return Math.random() > 0.5 ? "foo" : "bar";
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}
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};
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obj.__lookupGetter__("foo")
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// (function (){return Math.random() > 0.5 ? "foo" : "bar"}) </code></pre>
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<h2 id="Description" name="Description">附注</h2>
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<p><code><strong>__lookupGetter__</strong></code> 方法是非标准的，我们应该使用标准中定义的方法来完成同样的事情，那就是 <a href="Reference/Global_Objects/Object/getOwnPropertyDescriptor" title="Object.getOwnPropertyDescriptor() 方法返回指定对象上一个自有属性对应的属性描述符。（自有属性指的是直接赋予该对象的属性，不需要从原型链上进行查找的属性）"><code>Object.getOwnPropertyDescriptor()</code></a> 方法：</p>
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<pre><code class="language-javascript">var obj = {
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get foo() {
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return Math.random() > 0.5 ? "foo" : "bar";
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}
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};
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Object.getOwnPropertyDescriptor(obj, "foo").get
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// (function (){return Math.random() > 0.5 ? "foo" : "bar"})
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</code></pre>
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<p>如果那个访问器属性是继承来的，你还需要使用 <a href="Reference/Global_Objects/Object/getPrototypeOf" title="Object.getPrototypeOf() 方法返回指定对象的原型（内部[[Prototype]]属性的值）。"><code>Object.getPrototypeOf()</code></a>：</p>
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<pre><code class="language-javascript">var obj = {};
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var prototype = Object.getPrototypeOf(obj);
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Object.getOwnPropertyDescriptor(prototype, "foo").get
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// function __proto__() {[native code]}
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</code></pre>
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<h2 id="Specifications" name="Specifications">规范</h2>
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<p>不属于任何规范。</p>
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<h2 id="浏览器兼容性">浏览器兼容性</h2>
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<p></p><div class="blockIndicator warning"><strong><a class="external" href="https://github.com/mdn/browser-compat-data" rel="noopener">We're converting our compatibility data into a machine-readable JSON format</a></strong>.
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This compatibility table still uses the old format,
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because we haven't yet converted the data it contains.
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<strong><a class="new" href="/zh-CN/docs/MDN/Contribute/Structures/Compatibility_tables" rel="nofollow">Find out how you can help!</a></strong></div>
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<div class="htab">
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<a id="AutoCompatibilityTable" name="AutoCompatibilityTable"></a>
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<ul>
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<li class="selected"><a>Desktop</a></li>
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<li><a>Mobile</a></li>
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</ul>
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</div><p></p>
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<div id="compat-desktop">
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<table class="compat-table">
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<tbody>
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<tr>
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<th>Feature</th>
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<th>Chrome</th>
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<th>Firefox (Gecko)</th>
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<th>Internet Explorer</th>
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<th>Opera</th>
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<th>Safari</th>
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</tr>
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<tr>
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<td>Basic support</td>
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<td><span style="color: #888;" title="Please update this with the earliest version of support.">(Yes)</span></td>
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<td><span style="color: #888;" title="Please update this with the earliest version of support.">(Yes)</span></td>
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<td><span style="color: rgb(255, 153, 0);" title="Compatibility unknown; please update this.">?</span></td>
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<td><span style="color: #888;" title="Please update this with the earliest version of support.">(Yes)</span></td>
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<td><span style="color: #888;" title="Please update this with the earliest version of support.">(Yes)</span></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 id="compat-mobile">
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<table class="compat-table">
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<tbody>
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<tr>
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<th>Feature</th>
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<th>Android</th>
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<th>Chrome for Android</th>
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<th>Firefox Mobile (Gecko)</th>
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<th>IE Mobile</th>
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<th>Opera Mobile</th>
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<th>Safari Mobile</th>
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</tr>
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<tr>
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<td>Basic support</td>
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<td><span style="color: #888;" title="Please update this with the earliest version of support.">(Yes)</span></td>
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<td><span style="color: #888;" title="Please update this with the earliest version of support.">(Yes)</span></td>
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<td><span style="color: #888;" title="Please update this with the earliest version of support.">(Yes)</span></td>
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<td><span style="color: rgb(255, 153, 0);" title="Compatibility unknown; please update this.">?</span></td>
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<td><span style="color: rgb(255, 153, 0);" title="Compatibility unknown; please update this.">?</span></td>
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<td><span style="color: #888;" title="Please update this with the earliest version of support.">(Yes)</span></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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<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/Object/__lookupSetter__" title="一个绑定了setter的特殊属性的函数引用。"><code>Object.prototype.__lookupSetter__()</code></a></li>
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<li><a class="new" href="Reference/Operators/get" rel="nofollow" title="此页面仍未被本地化, 期待您的翻译!"><code>get</code></a> 运算符</li>
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<li><a href="Reference/Global_Objects/Object/getOwnPropertyDescriptor" title="Object.getOwnPropertyDescriptor() 方法返回指定对象上一个自有属性对应的属性描述符。（自有属性指的是直接赋予该对象的属性，不需要从原型链上进行查找的属性）"><code>Object.getOwnPropertyDescriptor()</code></a> 和 <a href="Reference/Global_Objects/Object/getPrototypeOf" title="Object.getPrototypeOf() 方法返回指定对象的原型（内部[[Prototype]]属性的值）。"><code>Object.getPrototypeOf()</code></a></li>
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<li><a href="Reference/Global_Objects/Object/__defineGetter__" title="__defineGetter__ 方法可以将一个函数绑定在当前对象的指定属性上，当那个属性的值被读取时，你所绑定的函数就会被调用。"><code>Object.prototype.__defineGetter__()</code></a></li>
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<li><a href="Reference/Global_Objects/Object/__defineSetter__" title="__defineSetter__ 方法可以将一个函数绑定在当前对象的指定属性上，当那个属性被赋值时，你所绑定的函数就会被调用。"><code>Object.prototype.__defineSetter__()</code></a></li>
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<li><a href="Guide/Working_with_Objects#Defining_getters_and_setters" title="JavaScript/Guide/Creating_New_Objects/Defining_Getters_and_Setters">JS 指南：定义访问器属性</a></li>
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</ul>
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</article> |