index.js
function isValid(checkNumber) {
    if (checkNumber == null) {
      return false;
    }
    var numbers = _splitDigits(checkNumber);
    return numbers.pop() === checkSum(numbers.join(''));
  }
function isValid(checkNumber) {
    if (checkNumber == null) {
      return false;
    }
    var numbers = _splitDigits(checkNumber);
    return numbers.pop() === checkSum(numbers.join(''));
  }
function isValid ( checkNumber ) { if ( checkNumber == null ) { return false ; } var numbers = _splitDigits ( checkNumber ) ; return numbers . pop ( ) === checkSum ( numbers . join ( '' ) ) ; }
validate num.

@param {string|number} checkNumber check number
@return {boolean} true: checkNumber is valid
validate num .