- $(window).blur()
jquery方法：
1.当内嵌iframe时，会触发
2.当弹出上传框时，会触发
3.当出现弹出“是否允许麦克风或摄像头”时，会触发
- document.hasFocus()：用于检测文档(或文档内的任一元素)是否获取焦点
1.当内嵌iframe时，不触发
2.当弹出上传框时，会触发
3.当出现弹出“是否允许麦克风或摄像头”时，会触发
| 方法 | chrome | ie | firefox | safari | opare |
|---|---|---|---|---|---|
| hasFocus() | 30.0 | 6.0 | 3.0 | Yes | 23.0 |
- document.activeElement:当前文档获取焦点的元素js对象
诡异问题：document.activeElement 为 HTMLBodyElement; 但 document.hasFocus() 返回 false；
场景描述：内嵌外部iframe页面，通过angular 路由跳转到parent window出现上面诡异问题；parent window页面跳转到内嵌iframe的页面正常；
解决方法：判断路由，非iframe路由强制focus button按钮
$("button#focus").get(0).focus();
猜测问题点：document.activeElement当页面没有焦点的时候 默认为 HTMLBodyElement;所以，iframe跳回主页面时并没有焦点；但是主页面跳转到iframe时会自动iframe获取焦点；
- 可以获取焦点的元素(浏览器行为，差异比较大)
- HTMLAnchorElement/HTMLAreaElement with an href
- HTMLInputElement/HTMLSelectElement/HTMLTextAreaElement/HTMLButtonElement but not with
disabled(IE actually gives you an error if you try), and file uploads have unusual behaviour for security reasons - HTMLIFrameElement (though focusing it doesn't do anything useful). Other embedding elements also, maybe, I haven't tested them all.
- Any element with a
tabindex != -1 - div contentEditable = true
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<style type="text/css">
.box{
100px;
height: 100px;
background-color: #EEEEEE;
display: inline-block;
}
</style>
<script type="text/javascript">
window.onload = function () {
document.onkeyup = function () {
console.log(document.activeElement);
}
}
</script>
</head>
<body>
<div class="box" tabindex="-1">tabindex = -1</div>
<div class="box" tabindex="2">tabindex = 2</div>
<span class="box" style="display: block"> display: block</span>
<div class="box" contenteditable="true">contenteditable="true"</div>
<button disabled>disabled</button>
<button>undisabled</button>
<iframe src="wwww.baidu.com" width="100" height="100"></iframe>
</body>
</html>