Call "new" programmatically in Coffeescript

Question

Possible Duplicate:
How do I make JavaScript Object using a variable String to define the class name?

I want to be able to call the new on things programmatically. So for example, if I have these two classes:

class Bird
   constructor: (@name) ->

class Snake
   constructor: (@name) ->

I can call s = new Snake("Sam"). Now, what I want to do is

bird_class = "Bird"
b = new bird_class()

and be able to construct a bird object from a string. Is this possible in CoffeeScript or Javascript?

Answer 1

If you kept your classes in an object you could always:

var animals = {
  Snake: Snake,
  Bird: Bird
};

new animals["Snake"]();

As per your comment, some pattern like this would let you register classes on the fly. It's raw, but might give you an idea:

var zoo = {
  animals: {},

  add: function (animal) {
    this.animals[animal.name] = animal;
  },

  make: function(name) {
    if (this.animals[name]) {
      return new this.animals[name]();
    }
  }
};

function Snake() {};
zoo.add(Snake);
var snake = zoo.make('Snake');