Fisher–Yates Shuffle algorithm

shuffle.coffee

#
# Fisher–Yates Shuffle algorithm
#
# Implementation by Danilo J. S. Bellini

randInt = (k) -> # From 0 to k (i.e., sample space has k + 1 values)
  Math.round Math.random() * k

shuffle = (data) ->
  for idx in [data.length-1..1]
    rnd = randInt idx
    [data[idx], data[rnd]] = [data[rnd], data[idx]]
  return data

# An example
console.log shuffle [0..5]

# In the shell:
# coffee shuffle.coffee 
# [ 3, 0, 4, 1, 5, 2 ]
#
# (Obviously the number ordering may vary...)