CoffeeScript mixins

gistfile1.coffee

# a.k.a. _.extend()
extend = (obj, mixin) ->
  for name, method of mixin
    obj[name] = method

include = (klass, mixin) ->
  extend klass.prototype, mixin

MyMixin =
  foo: -> 'bar'


## external ##

class User

include User, MyMixin

u = new User()
alert u.foo()


## internal ##

class Base
  @include: (mixin) ->
    include @, mixin

class Post extends Base

Post.include MyMixin

p = new Post()
alert p.foo()