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+---
+title: 'Array.prototype[@@unscopables]'
+slug: Web/JavaScript/Reference/Global_Objects/Array/@@unscopables
+tags:
+ - Array
+ - ECMAScript 2015
+ - JavaScript
+ - Property
+ - Prototype
+translation_of: Web/JavaScript/Reference/Global_Objects/Array/@@unscopables
+---
+<div>{{JSRef}}</div>
+
+<p>Symbol 属性 <code><strong>@@unscopable</strong></code> 包含了所有 ES2015 (ES6) 中新定义的、且并未被更早的 ECMAScript 标准收纳的属性名。这些属性被排除在由 <code><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/with">with</a></code> 语句绑定的环境中。</p>
+
+<h2 id="语法">语法</h2>
+
+<pre class="brush: js"><var>arr</var>[Symbol.unscopables]</pre>
+
+<h2 id="描述">描述</h2>
+
+<p><code>with</code> 绑定中未包含的数组默认属性有:</p>
+
+
+
+<ul>
+ <li>{{jsxref("Array.prototype.copyWithin()", "copyWithin()")}}</li>
+ <li>{{jsxref("Array.prototype.entries()", "entries()")}}</li>
+ <li>{{jsxref("Array.prototype.fill()", "fill()")}}</li>
+ <li>{{jsxref("Array.prototype.find()", "find()")}}</li>
+ <li>{{jsxref("Array.prototype.findIndex()", "findIndex()")}}</li>
+ <li>{{jsxref("Array.prototype.includes()", "includes()")}}</li>
+ <li>{{jsxref("Array.prototype.keys()", "keys()")}}</li>
+ <li>{{jsxref("Array.prototype.values()", "values()")}}</li>
+</ul>
+
+<p>参考 {{jsxref("Symbol.unscopables")}} 以了解如何为自定义的对象设置 <code>unscopables</code>。</p>
+
+<p>{{js_property_attributes(0,0,1)}}</p>
+
+<h2 id="示例">示例</h2>
+
+<p>以下的代码在 ES5 或更早的版本中能正常工作。然而 ECMAScript 2015 (ES6) 或之后的版本中新添加了 {{jsxref("Array.prototype.keys()")}} 这个方法。这意味着在 <code>with</code> 语句的作用域中,"keys"只能作为方法,而不能作为某个变量。这正是内置的 <code>@@unscopables</code> 即 <code>Array.prototype[@@unscopables]</code> symbol 属性所要解决的问题:防止某些数组方法被添加到 <code>with</code> 语句的作用域内。</p>
+
+<pre class="brush: js">var keys = [];
+
+with(Array.prototype) {
+ keys.push("something");
+}
+
+Object.keys(Array.prototype[Symbol.unscopables]);
+// ["copyWithin", "entries", "fill", "find", "findIndex",
+// "includes", "keys", "values"]</pre>
+
+<h2 id="规范">规范</h2>
+
+<table class="standard-table">
+ <tbody>
+ <tr>
+ <th scope="col">规范名称</th>
+ <th scope="col">规范状态</th>
+ <th scope="col">备注</th>
+ </tr>
+ <tr>
+ <td>{{SpecName('ES6', '#sec-array.prototype-@@unscopables', 'Array.prototype[@@unscopables]')}}</td>
+ <td>{{Spec2('ES6')}}</td>
+ <td>首次定义</td>
+ </tr>
+ <tr>
+ <td>{{SpecName('ESDraft', '#sec-array.prototype-@@unscopables', 'Array.prototype[@@unscopables]')}}</td>
+ <td>{{Spec2('ESDraft')}}</td>
+ <td></td>
+ </tr>
+ </tbody>
+</table>
+
+<h2 id="浏览器兼容性">浏览器兼容性</h2>
+
+<div>
+
+
+<p>{{Compat("javascript.builtins.Array.@@unscopables")}}</p>
+</div>
+
+<h2 id="相关链接">相关链接</h2>
+
+<ul>
+ <li>{{jsxref("Symbol.unscopables")}}</li>
+</ul>