inheritance.js

function Computer(make,model){
	this.make = make;
	this.model = model;
}

Computer.prototype.switchOn = function(){
	console.log("Switching on your " + this.model + ".");
}

Computer.prototype.switchOff = function(){
	console.log("Switching off your " + this.model + ".");
}

function OS(version, make, model){
	Computer.call(this, make, model);
	this.currentVersion = version;
}

OS.prototype = Object.create(Computer.prototype);

OS.prototype.update = function(version){
	console.log("Updating your " + this.model + " OS from " + this.currentVersion + " to " + version + ".");
	this.completed();
}

OS.prototype.completed = function(){
	console.log("Upgrade complete.")
}

var imac = new OS("10.8", "Apple", "iMac");

imac.switchOn();
imac.update("10.9");
imac.switchOff();