coffeescript implementation of extending Number with an ordinalize() method

ordinalize.coffee

Number::ordinal = ->
  return 'th' if 11 <= this % 100 <= 13
  switch this % 10
    when 1 then 'st'
    when 2 then 'nd'
    when 3 then 'rd'
    else        'th'

Number::ordinalize = ->
  this + this.ordinal()

1.ordinalize()   # => '1st'
2.ordinalize()   # => '2nd'
3.ordinalize()   # => '3rd'
4.ordinalize()   # => '4th'
11.ordinalize()  # => '11th'
12.ordinalize()  # => '12th'
13.ordinalize()  # => '13th'
21.ordinalize()  # => '21st'
22.ordinalize()  # => '22nd'
23.ordinalize()  # => '23rd'
100.ordinalize() # => '100th'
101.ordinalize() # => '101st'