Javascript interfaces revisited 2

interface-2.js

//a car factory
var CarFactory = { 
  getTires: function() {
    if(weather.raining) {
      return new WetTireSet();  
    }
    else {
      return new SlickTireSet();
    }      
  }
};
//creating the car
var redBull = new RaceCar("Red Bull");  
var tires = CarFactory.getTires();
redBull.fitTires(tires);