text: /**
   * Given a number, replace this number with
   * the sum of its digits until we get to a one digit number.
   *
   * @param {Number} n
   * @return {Number}
   *
   * @example
   * For 100, the result should be 1 (1 + 0 + 0 = 1)
   * For 91, the result should be 1 (9 + 1 = 10, 1 + 0 = 1)
   *
   */
  function getSumOfDigits(n) {
    let str = `${n}`;
    str = str.split('').map((i) => +i).reduce((sum, current) => sum + current);
    return str < 10 ? str : getSumOfDigits(str);
  }
  
  module.exports = getSumOfDigits;
  