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Luhn algorithm in Javascript. Check valid credit card numbers
// takes the form field value and returns true on valid number
function valid_credit_card(value) {
// accept only digits, dashes or spaces
if (/[^0-9-\s]+/.test(value)) return false;
// The Luhn Algorithm. It's so pretty.
var nCheck = 0, nDigit = 0, bEven = false;
value = value.replace(/\D/g, "");
for (var n = value.length - 1; n >= 0; n--) {
var cDigit = value.charAt(n),
nDigit = parseInt(cDigit, 10);
if (bEven) {
if ((nDigit *= 2) > 9) nDigit -= 9;
nCheck += nDigit;
bEven = !bEven;
return (nCheck % 10) == 0;

Nicely worked.


Tested with all the test card numbers from

Worked with all. Good job!


anyone have the generate algorithm? I need to generate ID numbers with a check digit


@Maxhodges - To generate a check digit, set bEven to true initially, and return (1000 - nCheck) % 10.


Execution time is very high: 35128.324ms

I've tried another Algorithm and it reported 0.059ms


Quite helpful !!


Thanks!!! great work! :smile:

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