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authorPeter Bengtsson <mail@peterbe.com>2020-12-08 14:40:17 -0500
committerPeter Bengtsson <mail@peterbe.com>2020-12-08 14:40:17 -0500
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+---
+title: NodeList.length
+slug: Web/API/NodeList/length
+tags:
+ - 属性
+translation_of: Web/API/NodeList/length
+---
+<div>{{APIRef("DOM")}}</div>
+
+<h2 id="Summary" name="Summary">摘要</h2>
+
+<p>返回 <a href="/zh-CN/docs/Web/API/NodeList">NodeList</a> <code>集合中</code>子节点数量<code>。</code></p>
+
+<h2 id="Syntax" name="Syntax">语法</h2>
+
+<pre class="brush: js"><em>numItems</em> =<em>nodeList</em>.length
+</pre>
+
+<ul>
+ <li><code>numItems</code> <code>是一个整数,表示</code> <code>NodeList</code> <code>子节点的数量。</code></li>
+</ul>
+
+<h2 id="Example" name="Example">例子</h2>
+
+<pre class="brush: js">// 获取文档中的所有 p 标签
+var items = document.getElementsByTagName("p");
+
+// 循环 items 然后输出每个 p 标签 html
+var gross = "";
+for (var i = 0; i &lt; items.length; i++) {
+ gross += items[i].innerHTML;
+}
+
+// gross 现在集合了所有 p 标签的 HTML 内容。
+</pre>
+
+<h2 id="Notes" name="Notes">注意</h2>
+
+<p>length 不是 <a href="en/DOM/element">元素(Element)</a>的属性,而是 <a href="/zh-CN/docs/Web/API/NodeList">NodeList</a> 的属性。NodeList 是使用 DOM 操作方法返回的对象,比如使用 <a href="en/DOM/document.getElementsByTagName">document.getElementsByTagName</a> 就会返回一个 NodeList 对象。</p>
+
+<p>length 是在 DOM 操作中非常常见的属性。最常见的是用 length 属性来判断某些节点是否存在,或者如上述一样,用在 for 循环上。</p>
+
+<h2 id="Specification" name="Specification">规范</h2>
+
+<p><a class="external" href="http://www.w3.org/TR/2000/REC-DOM-Level-2-Core-20001113/core.html#ID-203510337">length</a></p>