---
title: ParentNode.firstElementChild
slug: orphaned/Web/API/ParentNode/firstElementChild
translation_of: Web/API/ParentNode/firstElementChild
original_slug: Web/API/ParentNode/firstElementChild
---
<p>{{ APIRef("DOM") }}</p>

<p><strong><code>ParentNode.firstElementChild</code></strong> 介面會會返回 <code>ParentNode</code>的第一個子元素(唯讀) ，如果該節點沒有子節點則返回<code>null</code>。</p>

<div class="note">
<p>This property was initially defined in the {{domxref("ElementTraversal")}} pure interface. As this interface contained two distinct set of properties, one aimed at {{domxref("Node")}} that have children, one at those that are children, they have been moved into two separate pure interfaces, {{domxref("ParentNode")}} and {{domxref("ChildNode")}}. In this case, <code>firstElementChild</code> moved to {{domxref("ParentNode")}}. This is a fairly technical change that shouldn't affect compatibility.</p>
</div>

<h2 id="Syntax_and_values" name="Syntax_and_values">語法</h2>

<pre class="syntaxbox">var <em>element</em> = node.firstElementChild;
</pre>

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

<pre class="brush: html">&lt;ul id="foo"&gt;
  &lt;li&gt;First  (1)&lt;/li&gt;
  &lt;li&gt;Second (2)&lt;/li&gt;
  &lt;li&gt;Third  (3)&lt;/li&gt;
&lt;/ul&gt;

&lt;script&gt;
var foo = document.getElementById('foo');
// yields: First  (1)
console.log(foo.firstElementChild.textContent);
&lt;/script&gt;
</pre>

<h2 id="適用於IE8_IE9_和_Safari的Polyfill">適用於IE8, IE9 和 Safari的Polyfill</h2>

<pre class="brush: js">// Overwrites native 'firstElementChild' prototype.
// Adds Document &amp; DocumentFragment support for IE9 &amp; Safari.
;(function(constructor) {
    if (constructor &amp;&amp;
        constructor.prototype &amp;&amp;
        constructor.prototype.firstElementChild == null) {
        Object.defineProperty(constructor.prototype, 'firstElementChild', {
            get: function() {
                var node, nodes = this.childNodes, i = 0;
                while (node = nodes[i++]) {
                    if (node.nodeType === 1) {
                        return node;
                    }
                }
                return null;
            }
        });
    }
})(window.Node || window.Element);
</pre>

<h2 id="規範">規範</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('DOM WHATWG', '#dom-parentnode-firstelementchild', 'ParentNode.firstElementChild')}}</td>
   <td>{{Spec2('DOM WHATWG')}}</td>
   <td>Split the <code>ElementTraversal</code> interface in {{domxref("ChildNode")}} and <code>ParentNode</code>. This method is now defined on the latter.<br>
    The {{domxref("Document")}} and {{domxref("DocumentFragment")}} implemented the new interfaces.</td>
  </tr>
  <tr>
   <td>{{SpecName('Element Traversal', '#attribute-firstElementChild', 'ElementTraversal.firstElementChild')}}</td>
   <td>{{Spec2('Element Traversal')}}</td>
   <td>Added its initial definition to the <code>ElementTraversal</code> pure interface and use it on {{domxref("Element")}}.</td>
  </tr>
 </tbody>
</table>

<h2 id="瀏覽器相容性">瀏覽器相容性</h2>



<p>{{Compat("api.ParentNode.firstElementChild")}}</p>

<h2 id="參見">參見</h2>

<ul>
 <li>{{domxref("NonDocumentTypeChildNode.nextElementSibling")}}</li>
 <li>{{domxref("ParentNode.lastElementChild")}}</li>
 <li>The {{domxref("ParentNode")}} and {{domxref("ChildNode")}} pure interfaces.</li>
 <li>
  <div class="syntaxbox">Object types implementing this pure interface: {{domxref("Document")}}, {{domxref("Element")}}, and {{domxref("DocumentFragment")}}.</div>
 </li>
</ul>