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---
title: document.activeElement
slug: Web/API/DocumentOrShadowRoot/activeElement
tags:
- DOM
- Focus
- Gecko
- HTML5
- NeedsTranslation
- 要更新
translation_of: Web/API/DocumentOrShadowRoot/activeElement
translation_of_original: Web/API/Document/activeElement
original_slug: Web/API/Document/activeElement
---
<div>{{ApiRef}}</div>
<h2 id="Summary" name="Summary">概要</h2>
<p>Returns the currently focused element, that is, the element that will get keystroke events if the user types any. This attribute is read only.</p>
<p>Often this will return an {{HTMLElement("input")}} or {{HTMLElement("textarea")}} object, if it has the text selection at the time. If so, you can get more detail by using the element's <code>selectionStart</code> and <code>selectionEnd</code> properties. Other times the focused element might be a {{HTMLElement("select")}} element (menu) or an {{HTMLElement("input")}} element, of <code>type</code> button, checkbox or radio.</p>
<div class="note"><strong>注記:</strong> On Mac, elements that aren't text input elements tend not to get focus assigned to them.</div>
<p>Typically a user can press the tab key to move the focus around the page among focusable elements, and use the space bar to activate it (press a button, choose a radio).</p>
<p>Do not confuse focus with a selection over the document, consisting mostly of static text nodes. See {{domxref("window.getSelection()")}} for that.</p>
<p>When there is no selection, the active element is the page's {{HTMLElement("body")}}.</p>
<p>{{Note("This attribute is part of the in-development HTML 5 specification.")}}</p>
<h2 id="Syntax" name="Syntax">構文</h2>
<pre>var curElement = document.activeElement;
</pre>
<h2 id="Example" name="Example">例</h2>
<pre class="brush: html"><!DOCTYPE HTML>
<html>
<head>
<script type="text/javascript" charset="utf-8">
function init() {
function onMouseUp(e) {
console.log(e);
var outputElement = document.getElementById('output-element');
var outputText = document.getElementById('output-text');
var selectedTextArea = document.<strong>activeElement</strong>;
var selection = selectedTextArea.value.substring(
selectedTextArea.<strong>selectionStart</strong>, selectedTextArea.<strong>selectionEnd</strong>);
outputElement.innerHTML = selectedTextArea.id;
outputText.innerHTML = selection;
}
document.getElementById("ta-example-one").addEventListener("mouseup", onMouseUp, false);
document.getElementById("ta-example-two").addEventListener("mouseup", onMouseUp, false);
}
</script>
</head>
<body onload="init()">
<div>
Select some text from one of the Textareas below:
</div>
<form id="frm-example" action="#" accept-charset="utf-8">
<textarea name="ta-example-one" id="ta-example-one" rows="8" cols="40">
This is Textarea Example One:
Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec tincidunt, lorem a porttitor molestie, odio nibh iaculis libero, et accumsan nunc orci eu dui.
</textarea>
<textarea name="ta-example-two" id="ta-example-two" rows="8" cols="40">
This is Textarea Example Two:
Fusce ullamcorper, nisl ac porttitor adipiscing, urna orci egestas libero, ut accumsan orci lacus laoreet diam. Morbi sed euismod diam.
</textarea>
</form>
Active Element Id: <span id="output-element"></span><br/>
Selected Text: <span id="output-text"></span>
</body>
</html>
</pre>
<p><a href="https://jsfiddle.net/w9gFj">JSFiddle で確認</a></p>
<h2 id="Notes" name="Notes">注記</h2>
<p>Originally introduced as a proprietary DOM extension in Internet Explorer 4, this property also is supported in Opera and Safari (as of version 4).</p>
<h2 id="Specification" name="Specification">仕様</h2>
<ul>
<li><a href="http://www.whatwg.org/specs/web-apps/current-work/#focus-management">Focus management </a></li>
</ul>
<h2 id="Browser_compatibility" name="Browser_compatibility">ブラウザ実装状況</h2>
<div>{{CompatibilityTable}}</div>
<div id="compat-desktop">
<table class="compat-table">
<tbody>
<tr>
<th>機能</th>
<th>Chrome</th>
<th>Firefox (Gecko)</th>
<th>Internet Explorer</th>
<th>Opera</th>
<th>Safari (WebKit)</th>
</tr>
<tr>
<td>基本サポート</td>
<td>2</td>
<td>3.0</td>
<td>4</td>
<td>9.6</td>
<td>4.0</td>
</tr>
</tbody>
</table>
</div>
<div id="compat-mobile">
<table class="compat-table">
<tbody>
<tr>
<th>機能</th>
<th>Android</th>
<th>Firefox Mobile (Gecko)</th>
<th>IE Phone</th>
<th>Opera Mobile</th>
<th>Safari Mobile</th>
</tr>
<tr>
<td>基本サポート</td>
<td>{{CompatUnknown}}</td>
<td>{{CompatUnknown}}</td>
<td>{{CompatUnknown}}</td>
<td>{{CompatUnknown}}</td>
<td>{{CompatUnknown}}</td>
</tr>
</tbody>
</table>
</div>
<p> </p>
|
