jQuery基本语法
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<script type="text/javascript" src="jQuery/jquery-3.3.1.min.js"></script >
</head>
<body>
<script type="text/javascript">
$(document).ready(function(){
$str="我是一个声明变量"
//alert($str);
$("div").hide()
$("button").click(function(){ $("div").show() })
})
</script >
<div style="width:100px; height:100px; background:#968;"></div>
<button>点击显示</button>
</body>
</html>