old_contents: import assertString from './util/assertString';
  
  /* eslint-disable max-len */
  const creditCard = /^(?:4[0-9]{12}(?:[0-9]{3})?|5[1-5][0-9]{14}|6(?:011|5[0-9][0-9])[0-9]{12}|3[47][0-9]{13}|3(?:0[0-5]|[68][0-9])[0-9]{11}|(?:2131|1800|35\d{3})\d{11})$/;
  /* eslint-enable max-len */
  
  export default function isCreditCard(str) {
    assertString(str);
    const sanitized = str.replace(/[^0-9]+/g, '');
    if (!creditCard.test(sanitized)) {
      return false;
    }
    let sum = 0;
    let digit;
    let tmpNum;
    let shouldDouble;
    for (let 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);
  }
  
new_contents: import assertString from './util/assertString';
  
  /* eslint-disable max-len */
  const creditCard = /^(?:4[0-9]{12}(?:[0-9]{3})?|5[1-5][0-9]{14}|6(?:011|5[0-9][0-9])[0-9]{12}|3[47][0-9]{13}|3(?:0[0-5]|[68][0-9])[0-9]{11}|(?:2131|1800|35\d{3})\d{11})|62[0-9]{5,}$/;
  /* eslint-enable max-len */
  
  export default function isCreditCard(str) {
    assertString(str);
    const sanitized = str.replace(/[^0-9]+/g, '');
    if (!creditCard.test(sanitized)) {
      return false;
    }
    let sum = 0;
    let digit;
    let tmpNum;
    let shouldDouble;
    for (let 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);
  }
  
subject: Fix issue #535: add validation for Union Pay credit cards