Polymorphism

function A() {
	//private members
	var x;
 
	//getter
	this.getX = function() {
		return x;
	}
 
	//setter
	this.setX = function(newX) {
		x = newX;
	}
}
 
A.prototype.DoIt = function(data) {
	console.log(data);
}
 
B.prototype = new A();// Define sub-class
B.prototype.constructor = B;
 
function B() {
	A.call(this);
}
 
B.prototype.DoIt = function(data) {
	A.prototype.DoIt.call(this, data);
	console.log(data);
}
 
var i = new B();