JavaScript class creation with private members

Question

I'm working on a utility to create classes in javascript. And it works, the problem is how to define private attributes.

This is the code

var OO = {

    Class:function(){

        var len = arguments.length;
        var data = arguments[len-1];



        var Klass;
        if (data.constructor === Object){
            Klass = function (){};

        } else {
            Klass = data.constructor;
            delete data.constructor;                
        }



        OO.extend(Klass.prototype,data); //Classic Extend Method


        return Klass;


    },
//Simple extend method, just what I need in this case
    extend: function(target, source){
            var prop;
            for (prop in source)
                target[prop] = source [prop];

    }
}

This is how it works

// first create a class
var person = OO.Class ({
constructor: function (name, age) {
this.name = name;
this.age = age;
},

name:'',
age:'',

getName: function () {
return this.name;
},

getAge: function () {
return this.age;
}

});

And here is the instance

var one = new Person ('josh', 22);

And the problem:

one.age / / returns 22
one.name / / returns josh

What I need is that these properties can only be accessed by methods like getName () and getAge ()

EDIT1: Added Extend Function

Answer 1

The closure is created by the constructor params, so this is all you need to do (edited AlienWebguy's code):

var Person = function(name, age){

    this.getName = function() {
        return name;
    };

    this.getAge = function() {
        return age;
    };

};

var john = new Person('johnathan', 33);

document.writeln(john.name);        // undefined
document.writeln(john.age);         // undefined
document.writeln(john.getName());   // johnathan
document.writeln(john.getAge());    // 33