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44 lines
2.6 KiB
HTML
44 lines
2.6 KiB
HTML
<article id="wikiArticle">
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<div></div>
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<h2 id="错误提示">错误提示</h2>
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<pre><code class="language-javascript">SyntaxError: applying the 'delete' operator to an unqualified name is deprecated (Firefox)
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SyntaxError: Delete of an unqualified identifier in strict mode. (Chrome)
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</code></pre>
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<h2 id="错误类型">错误类型</h2>
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<p><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> 仅出现在<a href="/en-US/docs/Web/JavaScript/Reference/Strict_mode">严格模式</a>下。</p>
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<h2 id="哪里出错了？">哪里出错了？</h2>
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<p>在 JavaScript 中，普通变量是不能通过 <code><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/delete">delete</a></code> 操作符来删除的。在严格模式下，试图去删除一个变量会报错，这是不允许的。</p>
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<p>delete 操作符只能用于删除对象中的属性。只有可配置的对象属性才“符合”被删除的条件。</p>
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<p>与一般流行的观点相反的是， delete 操作符与直接释放内存<strong>无关</strong>。内存管理是通过切断引用来间接实现的。可以参考<a href="https://developer.mozilla.orgMemory_Management">内存管理</a>页面与 <a href="https://developer.mozilla.orgReference/Operators/delete">delete </a>操作符页面来获取更多的细节信息。</p>
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<p>这个错误提示只出现于<a href="/en-US/docs/Web/JavaScript/Reference/Strict_mode">严格模式</a>。在非严格模式下，该操作返回 false。</p>
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<h2 id="示例">示例</h2>
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<p>在 JavaScript 中，普通变量是不能删除的，在严格模式下会报错：</p>
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<pre><code class="language-js example-bad">'use strict';
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var x;
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// ...
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delete x;
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// SyntaxError: applying the 'delete' operator to an unqualified name
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// is deprecated
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</code></pre>
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<p>要释放变量引用的内容，可以将变量值设置为 <a href="Reference/Global_Objects/null" title="值 null 特指对象的值未设置。它是 JavaScript 基本类型 之一。"><code>null</code></a>:</p>
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<pre><code class="language-js example-good">'use strict';
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var x;
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// ...
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x = null;
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// x can be garbage collected
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</code></pre>
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<h2 id="相关内容">相关内容</h2>
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<ul>
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<li><code><a href="/en-US/docs/Web/JavaScript/Reference/Operators/delete">delete</a></code></li>
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<li><a href="/en-US/docs/Web/JavaScript/Memory_Management">内存管理</a></li>
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<li><a href="/en-US/docs/Web/JavaScript/Reference/Errors/Cant_delete">TypeError: property "x" is non-configurable and can't be deleted</a></li>
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</ul>
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</article> |