Beginning Web Development, Silverlight, and ASP.NET AJAX

CHAPTER 14 ■ JAVASCRIPT PROGRAMMING WITH ASP.NET AJAX 339
types of boat, such as a speedboat, a yacht, a cruise liner, and so on. These all have something
in common—that which makes them a boat—and something distinct, be it a
motor, a sail, or a movie theater. Thus, the concept of inheritance means we can define a
Boat class that contains the commonality and derive a SpeedBoat, Yacht, or CruiseShip
class from this using inheritance.
Listing 14-3 demonstrates this, extending the Boat class that you defined earlier, and
adding an outboard engine plus methods to activate it, giving us a speedboat.
Listing 14-3. Using an Inherited Class
Vehicles.SpeedBoat = function(boatSize, boatType, boatName, engineType)
{
Vehicles.SpeedBoat.initializeBase(this,[boatSize, boatType, boatName]);
this._engineType = engineType;
this._currentSpeed = 0;
}
Vehicles.SpeedBoat.prototype = {
getEngineType: function(){
return this._engineType;
},
setEngineType: function(){
this._engineType = engineType;
} ,
checkEngine: function(){
if (this._currentSpeed>0)
return ("Engine is running at speed" + this._currentSpeed);
else
return "Engine is off";
},
startEngine: function(){
if(this._currentSpeed == 0)
this._currentSpeed = 1;
else
return "Engine is already running";
},
openThrottle: function(){
if (this._currentSpeed0)
this._currentSpeed--;