[javascript patterns] Factory.

gistfile1.js

var CarMaker = function () {};

CarMaker.prototype.introduce = function () {
  console.log("This is " + this.title);
};

CarMaker.factory = function (type) {
  var constr = type,
      newcar;
  
  if (typeof CarMaker[constr] !== 'function') {
    throw {
      name: 'Error',
      message: "Constr " + constr + "doesn't exist"
    };
  }
  
  if (typeof CarMaker[constr].prototype.introduce !== 'function') {
    CarMaker[constr].prototype = new CarMaker();
  }
  
  newcar = new CarMaker[constr]();
  return newcar;
};

CarMaker.Daewoo = function () {
  this.title = "Daewoo";
};

CarMaker.Ford = function () {
  this.title = "Ford";
};

// usage
var daewoo = CarMaker.factory('Daewoo');
daewoo.introduce();