activeElement
只读特性在
Document
and
ShadowRoot
interfaces returns the
元素
within the DOM or shadow DOM tree that currently has focus.
Often
activeElement
will return a
HTMLInputElement
or
HTMLTextAreaElement
object if it has the text selection at the time. If so, you can get more detail by using the object's
selectionStart
and
selectionEnd
properties. Other times the focused element might be a
<select>
element (menu) or an
<input>
element, of
type
"button"
,
"checkbox"
，或
"radio"
.
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 one (that is, to press a button or toggle a radio button). Which elements are focusable varies depending on the platform and the browser's current configuration. For example, on macOS systems, elements that aren't text input elements are not typically focusable by default.
注意：
Focus (which element is receiving user input events) is not the same thing as selection (the currently highlighted part of the document). You can get the current selection using
window.getSelection()
.
element = DocumentOrShadowRoot.activeElement
元素
which currently has focus,
<body>
or
null
if there is no focused element.
<p>Select some text from one of the text areas below:</p> <form> <textarea name="ta-example-one" id="ta-example-one" rows="7" cols="40">This is Text Area 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="7" cols="40">This is Text Area Two. Fusce ullamcorper, nisl ac porttitor adipiscing, urna orci egestas libero, ut accumsan orci lacus laoreet diam. Morbi sed euismod diam.</textarea> </form> <p>Active element ID: <b id="output-element"></b></p> <p>Selected text: <b id="output-text"></b></p>
function onMouseUp(e) {
const activeTextarea = document.activeElement;
const selection = activeTextarea.value.substring(
activeTextarea.selectionStart, activeTextarea.selectionEnd
);
const outputElement = document.getElementById('output-element');
const outputText = document.getElementById('output-text');
outputElement.innerHTML = activeTextarea.id;
outputText.innerHTML = selection;
}
const textarea1 = document.getElementById('ta-example-one');
const textarea2 = document.getElementById('ta-example-two');
textarea1.addEventListener('mouseup', onMouseUp, false);
textarea2.addEventListener('mouseup', onMouseUp, false);
| 规范 | 状态 | 注释 |
|---|---|---|
|
HTML 实时标准
The definition of 'activeElement' in that specification. |
实时标准 |
| 桌面 | 移动 | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
activeElement
|
Chrome 53 | Edge 12 | Firefox 63 | IE 4 | Opera 40 | Safari 4 | WebView Android 53 | Chrome Android 53 | Firefox Android 63 | Opera Android 41 | Safari iOS 3.2 | Samsung Internet Android 6.0 |
完整支持
实验。期望将来行为有所改变。