Question about the vehicle factory example

Won't [this line](https://github.com/addyosmani/essential-js-design-patterns/blob/master/book/index.html#L3038) of the example change the default vehicle class for the next `createVehicle` call?

Here is the code

Brought the code here. I put a comment to point the line I'm taling about, it's near the end.

```js
// A constructor for defining new cars
function Car( options ) {

// some defaults
this.doors = options.doors || 4;
this.state = options.state || "brand new";
this.color = options.color || "silver";

}

// A constructor for defining new trucks
function Truck( options){

this.state = options.state || "used";
this.wheelSize = options.wheelSize || "large";
this.color = options.color || "blue";
}


// FactoryExample.js

// Define a skeleton vehicle factory
function VehicleFactory() {}

// Define the prototypes and utilities for this factory

// Our default vehicleClass is Car
VehicleFactory.prototype.vehicleClass = Car;

// Our Factory method for creating new Vehicle instances
VehicleFactory.prototype.createVehicle = function ( options ) {

switch(options.vehicleType){
case "car":
this.vehicleClass = Car;
break;
case "truck":
this.vehicleClass = Truck; // <------------------- THIS LINE /!\
break;
//defaults to VehicleFactory.prototype.vehicleClass (Car)
}

return new this.vehicleClass( options );
};
```