Sha256: 31abd5a6b83b3ff9a28806629dfe5cd3da459009b06d5fb9d956135c9ff16db5
Contents?: true
Size: 836 Bytes
Versions: 7
Compression:
Stored size: 836 Bytes
Contents
# Use the Luhn algorithm to validate a numeric identifier, such as credit card
# numbers, national insurance numbers, etc.
# See: http://en.wikipedia.org/wiki/Luhn_algorithm
is_valid_identifier: (identifier) ->
sum: 0
alt: false
for i in [(identifier.length - 1)..0]
# Get the next digit.
num: parseInt(identifier.charAt(i), 10)
# If it's not a valid number, abort.
return false if isNaN(num)
# If it's an alternate number...
if alt
num *= 2
num: (num % 10) + 1 if num > 9
# Flip the alternate bit.
alt: !alt
# Add to the rest of the sum.
sum += num
# Determine if it's valid.
sum % 10 is 0
# Tests.
puts(is_valid_identifier("49927398716") is true)
puts(is_valid_identifier("4408041234567893") is true)
puts(is_valid_identifier("4408041234567890") is false)
Version data entries
7 entries across 7 versions & 1 rubygems