<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
<script type="text/javascript">
var oldlee = 100;
var oldwang = 200;
// 变量
var oldzhao = oldlee + oldwang;
var oldlee = 0;
var oldwang = 0;
// 常量
const PI = 3.14;
PI = 200;
console.log("hello,node")
var a = 100; //全局变量(公有)
let b = 200; //局部变量(私有)
</script>
</head>
<body>
<div>hello</div>
</body>
</html>
//赋值过程叫复制
//关键字 变量 = 初值(字面量)
// const 常量 = 初值 常量就不可以改变的变量
//键对值 key = value