Creates a UUID and returns it.

uuid.coffee

# Filed under: uuid, id, random

###
  a: placeholder
###
b = (a) ->
  ###
    if the placeholder was passed, return a random number from 0 to 15 unless b
    is 8, in which case a random number from 8 to 11 in hexadecimal or
    otherwise a concatenated string: 10000000 + -1000 + -4000 + -80000000 +
    -100000000000, replacing zeroes, ones, and eights with random hex digits
  ###
  if a
    (a ^ Math.random() * 16 >> a / 4).toString(16)
  else
    ([1e7] + -1e3 + -4e3 + -8e3 + -1e11).replace(/[018]/g, b)