js2coffee sample http://js2coffee.org/ (javascript pattern observer sample)

observer.js.coffee

makePublisher = (o) ->
  i = undefined
  for i of publisher
    o[i] = publisher[i]  if publisher.hasOwnProperty(i) and typeof publisher[i] is "function"
  o.subscribers = any: []

publisher =
  subscribers:
    any: []

  subscribe: (fn, type) ->
    type = type or "any"
    @subscribers[type] = []  if typeof @subscribers[type] is "undefined"
    @subscribers[type].push fn

  unsubscribe: (fn, type) ->
    @visitSubscribers "unsubscribe", fn, type

  publish: (publication, type) ->
    @visitSubscribers "publish", publication, type

  visitSubscribers: (action, arg, type) ->
    pubtype = type or "any"
    subscribers = @subscribers[pubtype]
    i = undefined
    max = subscribers.length
    i = 0
    while i < max
      if action is "publish"
        subscribers[i] arg
      else
        subscribers.splice i, 1  if subscribers[i] is arg
      i += 1

paper =
  daily: ->
    @publish "big news today"

  monthly: ->
    @publish "interesting analysis", "monthly"

makePublisher paper

joe =
  drinkCoffee: (paper) ->
    console.log "Just read " + paper

  sundayPreNap: (monthly) ->
    console.log "About to fall asleep reading this " + monthly

paper.subscribe joe.drinkCoffee
paper.subscribe joe.sundayPreNap, "monthly"
paper.daily()
paper.daily()
paper.daily()
paper.monthly()