DistroHard/node_modules/validator/es/lib/isCreditCard.js

import assertString from './util/assertString';
/* eslint-disable max-len */

var creditCard = /^(?:4[0-9]{12}(?:[0-9]{3,6})?|5[1-5][0-9]{14}|(222[1-9]|22[3-9][0-9]|2[3-6][0-9]{2}|27[01][0-9]|2720)[0-9]{12}|6(?:011|5[0-9][0-9])[0-9]{12,15}|3[47][0-9]{13}|3(?:0[0-5]|[68][0-9])[0-9]{11}|(?:2131|1800|35\d{3})\d{11}|6[27][0-9]{14}|^(81[0-9]{14,17}))$/;
/* eslint-enable max-len */

export default function isCreditCard(str) {
  assertString(str);
  var sanitized = str.replace(/[- ]+/g, '');

  if (!creditCard.test(sanitized)) {
    return false;
  }

  var sum = 0;
  var digit;
  var tmpNum;
  var shouldDouble;

  for (var i = sanitized.length - 1; i >= 0; i--) {
    digit = sanitized.substring(i, i + 1);
    tmpNum = parseInt(digit, 10);

    if (shouldDouble) {
      tmpNum *= 2;

      if (tmpNum >= 10) {
        sum += tmpNum % 10 + 1;
      } else {
        sum += tmpNum;
      }
    } else {
      sum += tmpNum;
    }

    shouldDouble = !shouldDouble;
  }

  return !!(sum % 10 === 0 ? sanitized : false);
}