flatten (convert multidimensional array to one dimensinal array) function written in CoffeeScript

flatten.coffee

#!coffee

#
# Convert multidimensional array to one dimensional array.
# Return an empty list when passed array is an empty list.
#
# Usage::
#
#   assert = require 'assert'
#   matrix = [
#       [0, 1, 2];
#       [3, 4, 5];
#       [6, 7, 8]
#   ]
#   assert.deepEqual flatten(matrix), [0, 1, 2, 3, 4, 5, 6, 7, 8]
#
flatten = (a) ->
    if a.length is 0 then return []
    a.reduce (lhs, rhs) -> lhs.concat rhs

# --- unittest via 'assert' module of node.js
unittest = ->
    assert = require 'assert'
    matrix = [
        [0, 1, 2];
        [3, 4, 5];
        [6, 7, 8]
    ]
    assert.deepEqual flatten(matrix), [0, 1, 2, 3, 4, 5, 6, 7, 8]
unittest()

Didn't work for IE8 for me.

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