waterfall.coffee

gistfile1.coffee

waterfall = (i, fs, callback) ->
  if fs.length is 0 then callback()
  else if fs.length is 1 then fs[0] i, callback
  else
    p = 0
    scroll = (e, o) ->
      if e then callback(e)
      else
        p += 1
        if p is fs.length - 1
          fs[p](o, callback)
        else
          fs[p](o, scroll)
    fs[p](i, scroll)

waterfall "H", [
  (i, c) -> c(null, i + "e")
  (i, c) -> c(null, i + "l")
  (i, c) -> c(null, i + "l")
  (i, c) -> c(null, i + "o")
], (e, o) -> console.log "Error:", e, "Output:", r

waterfall "O", [
  (i, c) -> c(null, i + "h")
  (i, c) -> c({name: 'Bugger', message: 'Somebody stop me'}, i + "noes")
  (i, c) -> console.log "This does not happen"; c(null, i)
], (e, o) -> console.log "Error:", e, "Output:", r

###
Error: null Output: Hello
Error: { name: 'Bugger', message: 'Somebody stop me' } Output: undefined
###