How to use the card-validator.expirationMonth function in card-validator

CreditCardForm.prototype._onSplitDateChange = function () {
  var validationResult;

  var month = this.get('expirationMonth.value');
  var year = this.get('expirationYear.value');

  var monthValidation = validator.expirationMonth(month);
  var yearValidation = validator.expirationYear(year);

  if (monthValidation.isValid && yearValidation.isValid) {
    validationResult = validator.expirationDate(month + year);

    this.set('expirationMonth.isValid', validationResult.isValid);
    this.set('expirationMonth.isPotentiallyValid', validationResult.isPotentiallyValid);
    this.set('expirationYear.isValid', validationResult.isValid);
    this.set('expirationYear.isPotentiallyValid', validationResult.isPotentiallyValid);
  } else {
    this.set('expirationMonth.isValid', monthValidation.isValid);
    this.set('expirationMonth.isPotentiallyValid', monthValidation.isPotentiallyValid);
    this.set('expirationYear.isValid', yearValidation.isValid);
    this.set('expirationYear.isPotentiallyValid', yearValidation.isPotentiallyValid);
  }
};