Question about the vehicle factory example

[alvarocastro]

Won't this line 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.

// 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 );
};

[nitink4472]

The default statement under switch can't be under comment (//).

[alvarocastro]

What I meant is that if I don't specify the vehicleType in the options object, I get a new vehicle of the tipe it was last created, and not of the defaulted type, becase in each createVehicle call, the this.vehicleClass is changed (if a type is provided)

vf.createVehicle(); // Returns a Car
vf.createVehicle({ vehicleClass: 'truck'}); // Returns a Truck
vf.createVehicle(); // Returns a Truck

What confuses me is: why change the value of this.vehicleClass and don't use it as a read-only?

Wouldn't this be more clear/predictive and less messy?

VehicleFactory.prototype.createVehicle = function ( options ) {
  let vehicleClass = this.vehicleClass;

  switch(options.vehicleType){
    case "car":
      vehicleClass = Car;
      break;
    case "truck":
      vehicleClass = Truck; // <------------------- THIS LINE /!\
      break;
  }
 
  return new vehicleClass( options );
};