对象之成员函数：
对象不仅只有属性，还要有行为（函数）
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
<script language="JavaScript" type="text/javascript">
function Person(name, age) {
//传递实参初始化属性
this.name = name;
this.age = age;
// 这就是一个公开的函数，这样的话浪费资源
this.show = function() {
document.write("名字=" + this.name + " " + "年龄=" + this.age + "<br/>");
}
this.add = function() {
var res = 0;
for(var i = 1; i <= 1000; i++) {
res += i;
}
return res;
}
}
var p1 = new Person("宋江", 90);
p1.show();
var p2 = new Person("李逵", 78);
p2.show();
document.write("res=" + p1.add());
</script>
</head>
<body>
</body>
</html>