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+---
+title: Symbol.iterator
+slug: Web/JavaScript/Reference/Global_Objects/Symbol/iterator
+tags:
+  - ECMAScript 2015
+  - JavaScript
+  - Property
+  - Symbol
+translation_of: Web/JavaScript/Reference/Global_Objects/Symbol/iterator
+---
+<div>{{JSRef}}</div>
+
+<p><strong>Symbol.iterator </strong>为每一个对象定义了默认的迭代器。该迭代器可以被 <code><a href="/zh-CN/docs/Web/JavaScript/Reference/Statements/for...of">for...of</a></code> 循环使用。</p>
+
+<div>{{js_property_attributes(0,0,0)}}</div>
+
+<h2 id="描述">描述</h2>
+
+<p>当需要对一个对象进行迭代时（<font><font>比如开始用于一个</font></font><code><font><font>for..of</font></font></code><font><font>循环中</font></font>），它的<code>@@iterator</code>方法都会在不传参情况下被调用，返回的<strong>迭代器</strong>用于获取要迭代的值。</p>
+
+<p>一些内置类型拥有默认的迭代器行为，其他类型（如 {{jsxref("Object")}}）则没有。下表中的内置类型拥有默认的<span style="font-family: consolas,monaco,andale mono,monospace;"><code>@@iterator</code></span>方法：</p>
+
+<ul>
+ <li>{{jsxref("Array.@@iterator", "Array.prototype[@@iterator]()")}}</li>
+ <li>{{jsxref("TypedArray.@@iterator", "TypedArray.prototype[@@iterator]()")}}</li>
+ <li>{{jsxref("String.@@iterator", "String.prototype[@@iterator]()")}}</li>
+ <li>{{jsxref("Map.@@iterator", "Map.prototype[@@iterator]()")}}</li>
+ <li>{{jsxref("Set.@@iterator", "Set.prototype[@@iterator]()")}}</li>
+</ul>
+
+<p>更多信息请参见<a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Iteration_protocols">迭代协议</a>。</p>
+
+<h2 id="示例">示例</h2>
+
+<h3 id="自定义迭代器">自定义迭代器</h3>
+
+<p>我们可以像下面这样创建自定义的迭代器：</p>
+
+<pre class="brush: js">var myIterable = {}
+myIterable[Symbol.iterator] = function* () {
+    yield 1;
+    yield 2;
+    yield 3;
+};
+[...myIterable] // [1, 2, 3]
+</pre>
+
+<h3 id="不符合标准的迭代器">不符合标准的迭代器</h3>
+
+<p>如果一个迭代器 <code>@@iterator</code> 没有返回一个迭代器对象，那么它就是一个不符合标准的迭代器，这样的迭代器将会在运行期抛出异常，甚至非常诡异的 Bug。</p>
+
+<pre class="brush: js">var nonWellFormedIterable = {}
+nonWellFormedIterable[Symbol.iterator] = () =&gt; 1
+[...nonWellFormedIterable] // TypeError: [] is not a function
+</pre>
+
+<h2 id="规范">规范</h2>
+
+<table class="standard-table">
+ <tbody>
+  <tr>
+   <th scope="col">Specification</th>
+   <th scope="col">Status</th>
+   <th scope="col">Comment</th>
+  </tr>
+  <tr>
+   <td>{{SpecName('ES2015', '#sec-symbol.iterator', 'Symbol.iterator')}}</td>
+   <td>{{Spec2('ES2015')}}</td>
+   <td>Initial definition.</td>
+  </tr>
+  <tr>
+   <td>{{SpecName('ESDraft', '#sec-symbol.iterator', 'Symbol.iterator')}}</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 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 href="https://github.com/mdn/browser-compat-data">https://github.com/mdn/browser-compat-data</a> and send us a pull request.</div>
+
+<p>{{Compat("javascript.builtins.Symbol.iterator")}}</p>
+
+<h2 id="相关链接">相关链接</h2>
+
+<ul>
+ <li><a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Iteration_protocols">迭代协议</a></li>
+ <li>{{jsxref("Array.@@iterator", "Array.prototype[@@iterator]()")}}</li>
+ <li>{{jsxref("TypedArray.@@iterator", "TypedArray.prototype[@@iterator]()")}}</li>
+ <li>{{jsxref("String.@@iterator", "String.prototype[@@iterator]()")}}</li>
+ <li>{{jsxref("Map.@@iterator", "Map.prototype[@@iterator]()")}}</li>
+ <li>{{jsxref("Set.@@iterator", "Set.prototype[@@iterator]()")}}</li>
+</ul>