abstract_factory.js

var abstractBallFactory = (function() {
  var types = {};
  return {
    getBall: function(type, customizations) {
      var constractor = types[type];
      return ( constractor ? new constractor(customizations) : null );
    },
    registerBall: function(type, constractor) {
      types[type] = constractor;
      return abstractBallFactory;
    }
  };
})();

var Ball = function (customizations) {
  this.radius = customizations.radius;
};
Ball.prototype = {
  diameter: function() { return this.radius * 2; }
};

var SoccerBall = Ball;
SoccerBall.prototype = Ball.prototype;

(function() {
  abstractBallFactory.registerBall("Brazuca", SoccerBall);
  var brazuca = abstractBallFactory.getBall("Brazuca", {radius: 4.3});
  console.log(brazuca.diameter());
})();