JavaScript Design pattern-- Abstract Factory partial Code query

A piece of code that abstracts the factory pattern in the book JavaScript Design pattern:

var VehicleFactory = function(subType, superType){
    if(typeof VehicleFactory[superType] === "function"){
        function F(){}; 
        F.prototype = new VehicleFactory[superType]();
        subType.constructor = subType; //
        subType.prototype = new F();//
    }else{
        throw new Error("");
    }
}

//
VehicleFactory.car = function{
    this.type = "car"
}
VehicleFactory.car.prototype = {
    getPrice:function(){
        return new Error("")
    }
}
//
VehicleFactory.Bus = function(){
     this.type="Bus";
}
VehicleFactory.Bus.prototype = {
    getPrice:function(){
        return new Error("")
    }, 
    getPassengerNum:function(){
         return new Error("");
     }
}
//:
var BMW = function(price){
    this.price = price
}
VehicleFactory(BMW, "car");

//
BMW.prototype.getPrice = function(){
    return this.price 
}
var bmw1 = new BMW(100000);
cosole.log(bwm1.getPrice());

question 1: what does it mean here? The constructor property should only be set on the prototype, and subType is the constructor of a class. Shouldn"t it be subType.prototype.constructor = subType? And this sentence should be put after subType.property = new F ()?

question 2: why is F used for transition here, and why can"t we just let subType.prototype = new VehicleFactory [superType] ()?