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Hybrid factory paradigm

Car.prototype.showColor = function () {

alert(this.color);

};

Car._initialized = true;

}

The constructor is identical until the line that checks if

typeof Car._initialized

is equal to

“unde-

fined”

. This line is the most important part of the dynamic prototype method. If this value is unde-

fined, the constructor continues on to define the methods of the object using the prototype paradigm

and then sets

Car._initialized

true

. If the value is defined (when it’s true, its

typeof

is Boolean),

then the methods aren’t created again. Simply put, this method uses a flag (

_initialized

) to deter-

mine if the prototype has been assigned any methods yet. The methods are only created and assigned

once, and to the delight of traditional OOP developers, the code looks more like class definitions in other

languages.

Hybrid factory paradigm

This paradigm is typically used as a workaround when the previous paradigms don’t work. Here, the

aim is to create a dummy constructor that simply returns a new instance of another type of object. The

code looks very similar to the class paradigm’s factory function:

function Car() {

var oTempCar = new Object;

oTempCar.color = “red”;

oTempCar.doors = 4;

oTempCar.mpg = 23;

oTempCar.showColor = function () {

alert(this.color)

};

return oTempCar;

}

Unlike the classic paradigm, this paradigm uses the

new

keyword to make it seem like an actual con-

structor is being called:

var car = new Car();

Because the

new

operator is called within the

Car()

constructor, the second

new

operator (called outside

of the constructor) is essentially ignored. The object created inside the constructor is passed back into the

variable

car

This paradigm has the same problems as the classic paradigm regarding memory management of object

methods. It is highly recommended that you avoid using this method unless absolutely necessary (see

Chapter 15, “XML in JavaScript,” for an example of such a case).

Chapter 3

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