为什么我按老师的代码写，却没有输出相应的值，name，age都是undefined呢？求帮助

源自：8-1 概念与继承

<!doctype html>

<html>

<head>

</head>

<body>

function Person(name,age){

this.name = name;

this.age = age;

}

Person.prototype.hi = function(){

document.write('Hi,my name is '+this.name+",I'm "+age+' years old now'+"<br>");

};

Person.prototype.LEGS_NUM = 2;

Person.prototype.ARMS_NUM = 2;

Person.prototype.walk = function(){

document.write(this.name+" is walking..."+"<br>");

};

function Student(name, age, className){

Person.call(this.name,age);

this.className = className;

}

Student.prototype = Object.create(Person.prototype);

Student.prototype.constructor = Student;

Student.prototype.hi = function(){

document.write('Hi,my name is '+this.name+",I'm "+age+' years old now, and from '+this.className+"<br>");

};

Student.prototype.learn = function(subject){

document.write(this.name+' is learning '+subject+' at '+this.className+"<br>");

};

var jack = new Student('Jack',10,'Class 1,Grade 3'+"<br>");

jack.hi();

document.write(jack.LEGS_NUM+"<br>");

jack.walk();

jack.learn('Chinese');

</script>

</body>

</html>

提问者：小不点fly 2016-03-30 10:50