通配符选择器
选择所有元素.
jQuery("*")
警告：除非被它自己使用，否则*选择器或通用选择器，其速度是极其慢的。
例子
查找文档中的每一个元素（包括 head, body 等）。 Note that if your browser has an extension/add-on enabled that inserts a
<script>
or
<link>
element into the DOM, that element will be counted as well.
<!DOCTYPE html>
<html>
<head>
<style>
h3 { margin: 0; }
div,span,p {
width: 80px;
height: 40px;
float:left;
padding: 10px;
margin: 10px;
background-color: #EEEEEE;
}
</style>
<script src="./static/js/jquery-3.5.0.js"></script>
</head>
<body>
<div>DIV</div>
<span>SPAN</span>
<p>P <button>Button</button></p>
<script>var elementCount = $("*").css("border","3px solid red").length;
$("body").prepend("<h3>" + elementCount + " elements found</h3>");</script>
</body>
</html>
查找document.body的所有元素所以像head，script等元素被排除在外。
<!DOCTYPE html>
<html>
<head>
<style>
h3 { margin: 0; }
div,span,p {
width: 80px;
height: 40px;
float:left;
padding: 10px;
margin: 10px;
background-color: #EEEEEE;
}
#test {
width: auto; height: auto; background-color: transparent;
}
</style>
<script src="./static/js/jquery-3.5.0.js"></script>
</head>
<body>
<div id="test">
<div>DIV</div>
<span>SPAN</span>
<p>P <button>Button</button></p>
</div>
<script>
var elementCount = $("#test").find("*").css("border","3px solid red").length;
$("body").prepend("<h3>" + elementCount + " elements found</h3>");</script>
</body>
</html>