files/zh-tw/web/api/document/head/index.html


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---
title: Document.head
slug: Web/API/Document/head
translation_of: Web/API/Document/head
---
<p>{{APIRef("DOM")}}</p>

<p>回傳當前文件的 {{HTMLElement("head")}} 元素。如果該文件有超過一個 <code>&lt;head&gt;</code> 元素，那只會回傳第一個 <code>&lt;head&gt;</code> 元素。</p>

<h2 id="Syntax" name="Syntax">語法</h2>

<pre class="syntaxbox"><em>var objRef</em> = document.head;
</pre>

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

<pre class="brush: js">// in HTML: &lt;head id="my-document-head"&gt;
var aHead = document.head;

alert(aHead.id); // "my-document-head";

alert( document.head === document.querySelector("head") ); // true
</pre>

<h2 id="備註">備註</h2>

<p><code>document.head</code> 是「唯讀」。若是想要將 <code>document.head</code> 改成別的值會失敗，這時有些瀏覽器不會告知任何錯誤訊息；有些，例如在 <a href="/zh-TW/docs/Web/JavaScript/Reference/Functions_and_function_scope/Strict_mode">ECMAScript Strict 模式下</a> 的 Gecko 瀏覽器，會給出 <code><a href="/zh-TW/docs/Web/JavaScript/Reference/Global_Objects/TypeError">TypeError</a></code> 異常。</p>

<h2 id="規範">規範</h2>

<table class="spectable standard-table">
 <tbody>
  <tr>
   <th scope="col">Specification</th>
   <th scope="col">Status</th>
   <th scope="col">Comment</th>
  </tr>
  <tr>
   <td>{{SpecName('HTML WHATWG','dom.html#dom-document-head','Document.head')}}</td>
   <td>{{Spec2('HTML WHATWG')}}</td>
   <td>Initial definition.</td>
  </tr>
  <tr>
   <td>{{SpecName('HTML5.1','dom.html#dom-document-head','Document.head')}}</td>
   <td>{{Spec2('HTML5.1')}}</td>
   <td> </td>
  </tr>
  <tr>
   <td>{{SpecName('HTML5 W3C','dom.html#dom-document-head','Document.head')}}</td>
   <td>{{Spec2('HTML5 W3C')}}</td>
   <td> </td>
  </tr>
 </tbody>
</table>

<h2 id="瀏覽器相容性">瀏覽器相容性</h2>

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

<div id="compat-desktop">
<table class="compat-table">
 <tbody>
  <tr>
   <th>Feature</th>
   <th>Chrome</th>
   <th>Edge</th>
   <th>Firefox (Gecko)</th>
   <th>Internet Explorer</th>
   <th>Opera</th>
   <th>Safari</th>
  </tr>
  <tr>
   <td>Basic support</td>
   <td>4.0</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatGeckoDesktop("2")}}</td>
   <td>9.0</td>
   <td>11.0</td>
   <td>5.0</td>
  </tr>
 </tbody>
</table>
</div>

<div id="compat-mobile">
<table class="compat-table">
 <tbody>
  <tr>
   <th>Feature</th>
   <th>Android</th>
   <th>Edge</th>
   <th>Firefox Mobile (Gecko)</th>
   <th>IE Mobile</th>
   <th>Opera Mobile</th>
   <th>Safari Mobile</th>
  </tr>
  <tr>
   <td>Basic support</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatGeckoMobile("2")}}</td>
   <td>9.0</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
  </tr>
 </tbody>
</table>
</div>

<h2 id="參見">參見</h2>

<ul>
 <li>{{domxref("document.body")}}</li>
</ul>