Document.hasFocus()

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句法
范例
规范
浏览器兼容性
另请参阅
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hasFocus() 方法在 Document interface returns a 布尔 value indicating whether the document or any element inside the document has focus. This method can be used to determine whether the active element in a document has focus.

When viewing a document, an element with focus is always the active element in the document, but an active element does not necessarily have focus. For example, an active element within a popup window that is not the foreground doesn't have focus.

句法

var focused = document.hasFocus();

返回值

false if the active element in the document has no focus; true if the active element in the document has focus.

范例

This example checks whether the document has focus every 300 milliseconds. To test the functionality of hasFocus() , click on the button to open a new window, and try switching between the two pages.

HTML

<p id="log">Awaiting focus check.</p>
<button onclick="openWindow()">Open a new window</button>

JavaScript

function checkPageFocus() {
  let body = document.querySelector('body');
  let log = document.getElementById('log');
  if (document.hasFocus()) {
    log.textContent = 'This document has the focus.';
    body.style.background = '#fff';
  }
  else {
    log.textContent = 'This document does not have the focus.';
    body.style.background = '#ccc';
  }
}
function openWindow() {
  window.open('https://developer.mozilla.org/', 'MDN', 'width=640,height=320,left=150,top=150');
}
// Check page focus every 300 milliseconds
setInterval(checkPageFocus, 300);

结果

规范

规范	状态	注释
HTML 实时标准 The definition of 'Document.hasFocus()' in that specification.	实时标准	初始定义

浏览器兼容性

The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request. 更新 GitHub 上的兼容性数据

	桌面						移动
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`hasFocus`	Chrome 1	Edge 12	Firefox 3	IE 6	Opera 15	Safari 4	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 14	Safari iOS 3.2	Samsung Internet Android 1.0

图例

完整支持

另请参阅

Using the Page Visibility API

元数据

最后修改： Mar 22, 2019

在此页

句法

返回值

范例

HTML

JavaScript

结果

规范

浏览器兼容性

图例

另请参阅

相关话题