Question

A factory class isn’t the end product I am looking for but it is basically my problem boiled down. I am looking for a class we’ll call foo that can be passed in another class bar as a parameter to its constructor such that when later calling fooInstance.create() it returns a new instance of bar. I can easily figure out how to make a fooInstance.create(bar) create an instance of bar. But that isn’t what I need. I need each instance of the factory class to create a specific type of object. so:

    fooCar = new foo(Car);
    fooTruck = new foo(Truck);
    myCar = fooCar.create();
    myTruck = fooTruck.create();

This would be something easily handled by Generics in c#. I either get errors or I end up screwing with the prototype of foo which then changes the type created by all instances of foo.

Answer 1

Just return a regular object from your factory, with just one create method:

function foo (Constructor) {
    return {
        create: function () {
            return new Constructor();
        }
    };
}

Check out the fiddle: http://jsfiddle.net/fR5Gz/1/