JavaScript invoking "super" functions

gistfile1.js

// define the Person Class
function Person(name) {
	this.name = name;
	this.hasSaidHello = false;
}

Person.prototype.walk = function(){
  alert ('I am walking!');
};
Person.prototype.sayHello = function(){
  alert ('hello I am a Person');
  this.hasSaidHello = true;
};

// define the Student class
function Student(name) {
  // Call the parent constructor
  Person.call(this, name);
};

// inherit Person
Student.prototype = new Person("aStudent");

// correct the constructor pointer because it points to Person
Student.prototype.constructor = Student;
 
// replace the sayHello method
Student.prototype.sayHello = function(){
  Person.prototype.sayHello.call(this);
  alert("But I am also a Student");
};

// add sayGoodBye method
Student.prototype.sayGoodBye = function(){
  alert('goodBye');
};

var student1 = new Student("John");
student1.sayHello();
student1.walk();
student1.sayGoodBye();

// check inheritance
alert(student1 instanceof Person); // true 
alert(student1 instanceof Student); // true
alert("Student1 has said Hello?: " + student1.hasSaidHello);
alert("Student1's name is " + student1.name);