Credit card number validating

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It will not, however, detect transposition of the two-digit sequence 09 to 90 (or vice versa).It will detect 7 of the 10 possible twin errors (it will not detect 22 ↔ 55, 33 ↔ 66 or 44 ↔ 77).If you're doing something to the input it should be obvious that it's happening and clear as to why it's being done.The Luhn algorithm or Luhn formula, also known as the "modulus 10" or "mod 10" algorithm, is a simple checksum formula used to validate a variety of identification numbers, such as credit card numbers, IMEI numbers, National Provider Identifier numbers in the United States, Canadian Social Insurance Numbers, Israel ID Numbers and Greek Social Security Numbers (ΑΜΚΑ). 2,950,048, filed on January 6, 1954, and granted on August 23, 1960.The substitution digits, that is, the results of the double and reduce procedure, were not produced mechanically.

The algorithm appeared in a US Patent for a hand-held, mechanical device for computing the checksum. The device took the mod 10 sum by mechanical means.Because the algorithm operates on the digits in a right-to-left manner and zero digits affect the result only if they cause shift in position, zero-padding the beginning of a string of numbers does not affect the calculation.Therefore, systems that pad to a specific number of digits (by converting 1234 to 0001234 for instance) can perform Luhn validation before or after the padding and achieve the same result.The reality is that some quite simple HTML, Java Script or even Ajax code can make a big difference in terms of reducing the number of requests to the server and keeping your users happy.The point of the above examples is to show how you can use a number of different techniques to filter form input.You can use the HTML attribute to restrict the number of input characters, filtering 'as you type' to limit or format input, and present 'feedback' to highlight where there might be problems before the form is submitted.

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