output.log

[parallel] time coffee usage.coffee
{ '0': 'response for /movies'
, '1': 'response for /books'
}
{ '0': 'response for /tv-shows'
, '1': 'response for /blogs'
}

real	0m1.234s
user	0m0.178s
sys	0m0.050s

parallel.coffee

exports.ize: (actions...,callback) ->
  results: []
  counter: actions.length
  cb: (result) ->
    results.push(result)
    callback.apply(null, results) if results.length == actions.length
  action(cb) for action in actions

usage.coffee

sys: require 'sys'
parallel: require './parallel'

# an async function that takes a callback as its last argument
fetch: (url, callback) ->
  setTimeout (-> callback "response for $url"), 1000

# To parallelize, either curry the async function:

Function::curry: ->
  self: this
  args: Array.prototype.slice.call(arguments)
  ->
    self.apply(this, args.concat(Array.prototype.slice.call(arguments)));

parallel.ize(
  fetch.curry('/movies'),
  fetch.curry('/books'),
  (movies,books) -> sys.puts sys.inspect arguments
)

# Or define a curried wrapper

parallel_fetch: (url) ->
  (callback) -> fetch(url, callback)

parallel.ize(
  parallel_fetch('/tv-shows'),
  parallel_fetch('/blogs'),
  (tv,blogs) -> sys.puts sys.inspect arguments
)