text: import { NotImplementedError } from '../extensions/index.js';
  
  /**
   * 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)
   *
   */
  export default function getSumOfDigits(n) {
    let ans = String(n);
    while (ans.length !== 1) {
      let sum = 0;
      for (let i = 0; i < ans.length; i++) {
        sum += Number(ans[i]);
      }
      ans = String(sum);
    }
  
    return Number(ans);
  }
  