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+---
+title: 'SyntaxError: "x" is a reserved identifier'
+slug: Web/JavaScript/Reference/Errors/Reserved_identifier
+tags:
+ - JavaScript
+ - 语法错误
+ - 错误
+translation_of: Web/JavaScript/Reference/Errors/Reserved_identifier
+---
+<div>{{jsSidebar("Errors")}}</div>
+
+<h2 id="消息提示">消息提示</h2>
+
+<pre class="syntaxbox">SyntaxError: "x" is a reserved identifier (Firefox)
+SyntaxError: Unexpected reserved word (Chrome)</pre>
+
+<h2 id="错误类型">错误类型</h2>
+
+<p>{{jsxref("SyntaxError")}}</p>
+
+<h2 id="哪里出错了?">哪里出错了?</h2>
+
+<p><a href="/en-US/docs/Web/JavaScript/Reference/Lexical_grammar#Keywords">保留字</a> 用作标记符将会出错. 这些标记符在严格模式和非严格模式下保留:</p>
+
+<ul>
+ <li><code>enum</code></li>
+</ul>
+
+<p>以下标记符只会在严格模式下才作为保留字:</p>
+
+<ul class="threecolumns">
+ <li><code>implements</code></li>
+ <li><code>interface</code></li>
+ <li>{{jsxref("Statements/let", "let")}}</li>
+ <li><code>package</code></li>
+ <li><code>private</code></li>
+ <li><code>protected</code></li>
+ <li><code>public</code></li>
+ <li><code>static</code></li>
+</ul>
+
+<h2 id="示例">示例</h2>
+
+<h3 id="严格与非严格模式下的保留字">严格与非严格模式下的保留字</h3>
+
+<p>在两种模式下,<code>enum</code> 标识符都会作为保留字。</p>
+
+<pre class="brush: js example-bad">var enum = { RED: 0, GREEN: 1, BLUE: 2 };
+// SyntaxError: enum is a reserved identifier
+</pre>
+
+<p>在严格模式下,会有更多的保留字。</p>
+
+<pre class="brush: js example-bad">"use strict";
+var package = ["potatoes", "rice", "fries"];
+// SyntaxError: package is a reserved identifier
+</pre>
+
+<p>你需要对上述变量重新命名。</p>
+
+<pre class="brush: js example-good">var colorEnum = { RED: 0, GREEN: 1, BLUE: 2 };
+var list = ["potatoes", "rice", "fries"];</pre>
+
+<h3 id="升级旧版本浏览器">升级旧版本浏览器</h3>
+
+<p>假如你还在使用尚未支持 let 或 class 等特性的旧版本浏览器,你应该将它们升级到支持这些新语言特性的版本。</p>
+
+<pre class="brush: js">"use strict";
+class DocArchiver {}
+
+// SyntaxError: class is a reserved identifier
+//(只会在旧版本浏览器中抛出,例如 Firefox 44 或更老的版本)
+</pre>
+
+<h2 id="相关内容">相关内容</h2>
+
+<ul>
+ <li><a href="http://wiki.c2.com/?GoodVariableNames">Good variable names</a></li>
+</ul>