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 sum;
    let num = n;
  
    do {
      sum = 0;
      while (num) {
        sum += num % 10;
        num = Math.floor(num / 10);
      }
      if (sum > 9) {
        num = sum;
      }
    } while (sum > 9);
  
    return sum;
  }
  
  module.exports = getSumOfDigits;
  