流れるようなインターフェイス

worker.coffee

class Worker
  constructor: ->
    @jobs = []

  register: (job) ->
    @jobs.push job

  work: ->
    job = do @jobs.shift
    return unless job
    job => do @work

worker = new Worker
worker.register (done) ->
  console.log "1 do"
  setTimeout ->
    console.log "1 done"
    do done
  , 1000

worker.register (done) ->
  console.log "2 do"
  setTimeout ->
    console.log "2 done"
    do done
  , 1000

worker.register (done) ->
  console.log "3 do"
  setTimeout ->
    console.log "3 done"
    do done
  , 1000

do worker.work