text: #!/usr/bin/env node
  /*
  Given a non-negative integer num, repeatedly add all its digits until
  the result has only one digit.
  
  Example:
  Input: 38
  Output: 2 
  Explanation: The process is like: 3 + 8 = 11, 1 + 1 = 2. 
               Since 2 has only one digit, return it.
  
  */
  
  function addDigits(num) {
      if(num < 10) return num;
      var reducer= (a, b) => a + parseInt(b);
      return addDigits(num.toString().split("").reduce(reducer, 0));
  }
  
  console.log(addDigits(38));
  