<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>字面量和变量</title>
<script type="text/javascript">
/*
字面量（常量），都是一些不可改变的值
比如 ：1 2 3 4 5 "hello"
*/
var a;//undefined
a = 123;
console.log(a);
var b = 789;
console.log(b);
var c = 0;
console.log(c);
var age = 80;
console.log(age)
</script>
</head>
<body>
</body>
</html>
