gistfile1.js

var MyNamespace = {};

MyNamespace.Person = function(){
  /* Public Fields */
  this.name = '';
  this.sex = 'M';
  /* Private Fields */
  var _age = 0;
  /* Constructor */
  this.initialize = function(name, sex, age){
    this.name = name;
    this.sex = sex;
    _age = age;
    return this;
  };
  /* Methods */
  this.getAge = function(){
    return _age;
  };
};

MyNamespace.Woman = function(){
  var parent = new MyNamespace.Person();
  parent.constructor.apply(this);
  /* Public Fields */
  this.sex = 'F';
  /* Constructor */
  this.initialize = function(name, age){
    parent.initialize.call(this, name, this.sex, age);
    return this;
  };
};

var she = (new MyNamespace.Woman()).initialize('Hanako', 25);