CoffeeScript Mixins, so easy to implement.

CoffeeScript Mxins

mixin = (Klass, Mixin) ->
  # Class methods
  Klass[key] = val for key, val of Mixin
  # Instance methods
  Klass::[key] = val for key, val of Mixin.prototype


class Mixin
  @fn: -> alert "class fn"
  fn:  -> alert "instance fn"

class Base
  baseClassFn: -> 'baseClassFn called'
  baseInstancefn: -> 'baseInstanceFn called'

mixin Base, Mixin

Base.fn() #'class fn' alerted
b = new Base
b.fn() #'instance fn' alerted