---
title: Headers()
slug: Web/API/Headers/Headers
tags:
  - Headers
  - Headers构造函数
translation_of: Web/API/Headers/Headers
---
<p>{{APIRef("Fetch")}}{{ SeeCompatTable() }}</p>

<p><code>使用<strong>Headers()</strong></code> 构造方法创建一个新的{{domxref("Headers")}} 对象.</p>

<h2 id="Syntax">Syntax</h2>

<pre class="brush: js">var myHeaders = new Headers(init);</pre>

<h3 id="Parameters">Parameters</h3>

<dl>
 <dt><em>init</em> {{optional_inline}}</dt>
 <dd>通过一个包含任意 <a href="/en-US/docs/Web/HTTP/Headers">HTTP headers</a> 的对象来预设你的 <code>Headers</code>. 可以是一个{{domxref("ByteString")}} 对象; 或者是一个已存在的 <code>Headers</code> 对象. </dd>
</dl>

<h2 id="Example">Example</h2>

<p>创建一个空的 <code>Headers</code> 对象:</p>

<pre class="brush: js">var myHeaders = new Headers(); // Currently empty</pre>

<p>你可以使用{{domxref("Headers.append")}}方法添加一个header并赋值:</p>

<pre class="brush: js">myHeaders.append('Content-Type', 'image/jpeg');
myHeaders.get('Content-Type'); // Returns 'image/jpeg'
</pre>

<p>或者你可以在Headers对象创建时添加多个header. 在下面的示例中我们创建了一个新的{{domxref("Headers")}} 对象, 并通过Headers构造函数中init属性来添加多个header:</p>

<pre class="brush: js">var httpHeaders = { 'Content-Type' : 'image/jpeg', 'Accept-Charset' : 'utf-8', 'X-My-Custom-Header' : 'Zeke are cool' };
var myHeaders = new Headers(httpHeaders);</pre>

<p><code><font face="Open Sans, Arial, sans-serif">你可以通过init属性将一个已存在的</font>Headers对象来创建另一个新的Headers对象</code>:</p>

<pre class="brush: js">var secondHeadersObj = new Headers(myHeaders);
secondHeadersObj.get('Content-Type'); // Would return 'image/jpeg' — it inherits it from the first headers object</pre>

<h2 id="Specifications">Specifications</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('Fetch','#dom-headers','Headers()')}}</td>
   <td>{{Spec2('Fetch')}}</td>
   <td> </td>
  </tr>
 </tbody>
</table>

<h2 id="Browser_compatibility">Browser compatibility</h2>

<p>{{ CompatibilityTable() }}</p>

<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 (WebKit)</th>
  </tr>
  <tr>
   <td>Basic support</td>
   <td>{{ CompatChrome(42) }}<br>
    {{ CompatChrome(41) }} behind pref<br>
     </td>
   <td>{{ CompatGeckoDesktop(39)}}<br>
    34 behind pref</td>
   <td>{{ CompatNo }}</td>
   <td>
    <p>29<br>
     28 behind pref</p>
   </td>
   <td>{{ CompatNo }}</td>
  </tr>
 </tbody>
</table>
</div>

<div id="compat-mobile">
<table class="compat-table">
 <tbody>
  <tr>
   <th>Feature</th>
   <th>Android</th>
   <th>Firefox Mobile (Gecko)</th>
   <th>Firefox OS (Gecko)</th>
   <th>IE Phone</th>
   <th>Opera Mobile</th>
   <th>Safari Mobile</th>
   <th>Chrome for Android</th>
  </tr>
  <tr>
   <td>Basic support</td>
   <td>{{ CompatNo }}</td>
   <td>{{ CompatNo }}</td>
   <td>{{ CompatNo }}</td>
   <td>{{ CompatNo }}</td>
   <td>{{ CompatNo }}</td>
   <td>{{ CompatNo }}</td>
   <td>{{ CompatNo }}</td>
  </tr>
 </tbody>
</table>
</div>

<h2 id="See_also">See also</h2>

<ul>
 <li><a href="/en-US/docs/Web/API/ServiceWorker_API">ServiceWorker API</a></li>
 <li><a href="/en-US/docs/Web/HTTP/Access_control_CORS">HTTP access control (CORS)</a></li>
 <li><a href="/en-US/docs/Web/HTTP">HTTP</a></li>
</ul>