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Luhn algorithm in Javascript. Check valid credit card numbers
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// Takes a credit card string 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. | |
let nCheck = 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 && (nDigit *= 2) > 9) nDigit -= 9; | |
nCheck += nDigit; | |
bEven = !bEven; | |
} | |
return (nCheck % 10) == 0; | |
} |
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