Mastering JavaScript

JavaScript Patterns
Let's take a common example to understand the usage of a factory. Let's say that we
have the following:
• A constructor, CarFactory()
• A static method in CarFactory called make() that knows how to create
objects of the car type
• Specific car types such as CarFactory.SUV, CarFactory.Sedan, and so on
We want to use CarFactory as follows:
var golf = CarFactory.make('Compact');
var vento = CarFactory.make('Sedan');
var touareg = CarFactory.make('SUV');
Here is how you would implement such a factory. The following implementation
is fairly standard. We are programmatically calling the constructor function that
creates an object of the specified type—CarFactory[const].prototype = new
CarFactory();.
We are mapping object types to the constructors. There can be variations in how you
can go about implementing this pattern:
// Factory Constructor
function CarFactory() {}
CarFactory.prototype.info = function() {
console.log("This car has "+this.doors+" doors and a
"+this.engine_capacity+" liter engine");
};
// the static factory method
CarFactory.make = function (type) {
var constr 0= type;
var car;
CarFactory[constr].prototype = new CarFactory();
// create a new instance
car = new CarFactory[constr]();
return car;
};
CarFactory.Compact = function () {
this.doors = 4;
this.engine_capacity = 2;
};
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