export default class StringCalculator {
  add(numbers) {
    if (numbers == undefined || numbers == null) {
      throw new Error("Wrong argument");
    }
    if (numbers.length == 0) {
      return 0;
    }

    const splitNumbers = numbers.split(/,|\n/).map(el => parseInt(el));
    if (splitNumbers.includes(NaN)) {
      throw new Error("Wrong argument");
    } else {
      return splitNumbers
        .map(text => parseInt(text))
        .reduce((acc, val) => val + acc, 0);
    }
  }
}