Prototype chain of JavaScrit.

Prototype chain is a inheritance system of JavaScript.
Prototype of sub class is instance of base class.

var Person = function() {};
Person.prototype = {
  name : "hoge",
  toString : function() {
    window.alert(this.name);
  }
};

var Programmer = function() {};
Programmer.prototype = new Person();

var shunsuk = new Programmer();
shunsuk.name = "shunsuk";
shunsuk.toString();