---
title: FormData.keys()
slug: Web/API/FormData/keys
translation_of: Web/API/FormData/keys
---
<p>{{APIRef("XMLHttpRequest")}}</p>

<p><code><strong>FormData.keys()</strong></code> 该方法返回一个迭代器（{{jsxref("Iteration_protocols",'iterator')}}），遍历了该 formData  包含的所有key ，这些 key 是 {{domxref("USVString")}} 对象。</p>

<div class="note">
<p><strong>注意</strong>: 该方法在 <a href="/en-US/docs/Web/API/Web_Workers_API">Web Workers</a> 可用。</p>
</div>

<h2 id="语法">语法</h2>

<pre class="syntaxbox">formData.keys();</pre>

<h3 id="返回值">返回值</h3>

<p>返回一个迭代器（ {{jsxref("Iteration_protocols","iterator")}}）。</p>

<h2 id="示例">示例</h2>

<pre class="brush: js;highlight:[7]">// 先创建一个 FormData 对象
var formData = new FormData();
formData.append('key1', 'value1');
formData.append('key2', 'value2');

// 输出所有的 key
for (var key of formData.keys()) {
   console.log(key);
}
</pre>

<p>结果如下：</p>

<pre>key1
key2</pre>

<h2 id="规范">规范</h2>

<table class="standard-table">
 <tbody>
  <tr>
   <th scope="col">规范</th>
   <th scope="col">状态</th>
   <th scope="col">说明</th>
  </tr>
  <tr>
   <td>{{SpecName('XMLHttpRequest','#dom-formdata','keys() (as iterator&lt;&gt;)')}}</td>
   <td>{{Spec2('XMLHttpRequest')}}</td>
   <td>Initial definition</td>
  </tr>
 </tbody>
</table>

<h2 id="浏览器兼容性">浏览器兼容性</h2>

<div>{{CompatibilityTable}}</div>

<div id="compat-desktop">
<table class="compat-table">
 <tbody>
  <tr>
   <th>Feature</th>
   <th>Chrome</th>
   <th>Firefox (Gecko)</th>
   <th>Internet Explorer</th>
   <th>Opera</th>
   <th>Safari</th>
  </tr>
  <tr>
   <td>Basic support</td>
   <td>{{CompatChrome(50.0)}}</td>
   <td>{{CompatGeckoDesktop(44)}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatUnknown}}</td>
  </tr>
  <tr>
   <td>Available in web workers</td>
   <td>{{CompatChrome(50.0)}}</td>
   <td>{{CompatGeckoDesktop(44)}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatUnknown}}</td>
  </tr>
 </tbody>
</table>
</div>

<div id="compat-mobile">
<table class="compat-table">
 <tbody>
  <tr>
   <th>Feature</th>
   <th>Android</th>
   <th>Android Webview</th>
   <th>Firefox Mobile (Gecko)</th>
   <th>IE Mobile</th>
   <th>Opera Mobile</th>
   <th>Safari Mobile</th>
   <th>Chrome for Android</th>
  </tr>
  <tr>
   <td>Basic support</td>
   <td>{{CompatNo}}</td>
   <td>{{CompatChrome(50.0)}}</td>
   <td>{{CompatGeckoMobile(44)}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatChrome(50.0)}}</td>
  </tr>
  <tr>
   <td>Available in web workers</td>
   <td>{{CompatNo}}</td>
   <td>{{CompatChrome(50.0)}}</td>
   <td>{{CompatGeckoMobile(44)}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatChrome(50.0)}}</td>
  </tr>
 </tbody>
</table>
</div>

<p> </p>

<h2 id="相关链接">相关链接</h2>

<ul>
 <li>{{domxref("XMLHTTPRequest")}}</li>
 <li><a href="/en-US/docs/DOM/XMLHttpRequest/Using_XMLHttpRequest" title="Using XMLHttpRequest">Using XMLHttpRequest</a></li>
 <li><a href="/en-US/docs/DOM/XMLHttpRequest/FormData/Using_FormData_Objects" title="DOM/XMLHttpRequest/FormData/Using_FormData_objects">Using FormData objects</a></li>
 <li>{{HTMLElement("Form")}}</li>
</ul>