child.js

//this works encapsulating private properties
//now, how about prototypes?

var Child = (function (s, f){
	var DOB = new Date();
	var sex = s;
	var fullName = f;
	var mood;
	
	return {
		getAge : function(){
			var now = new Date();
			var age = now.getFullYear() - DOB.getFullYear();
			var m = now.getMonth() - DOB.getMonth();
			if (m < 0 || (m === 0 && now.getDate() < DOB.getDate())) {
				age--;
			}
			return age;
		},
		sayHi : function(){
			return "Chichi wa saikōdesu! " + fullName + " love you so much!";
		},
		kissu : function(){
			var response = (mood === "happy") ? "ottosan motto, motto, mottttooooo~" : 
				"Anata wa saiakuda";
			return response;   
		},
		getDOB : function(){
			return DOB.valueOf();
		}	
	}
});
 
var ilya = new Child('F', 'Ilyasviel von Einzbern');
var araragi = new Child('M', 'Araragi Koyomi');

console.log(ilya.sayHi());
console.log(ilya.getDOB());
console.log(araragi.sayHi());
console.log(araragi.getDOB());