LeetCode-Codewars/SumOfDigits.js at master · evrenkaraarslan/LeetCode-Codewars · GitHub

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function digital_root(n) {
    let sum=10;
    while(sum>9) {
      n=n.toString();
      sum=0;
      for(let i=0;i<n.length;i++){
      sum+=parseInt(n[i]); }
      n=sum;}
      return sum;}
/*

In this kata, you must create a digital root function.

A digital root is the recursive sum of all the digits in a number.
Given n, take the sum of the digits of n. If that value has more
than one digit, continue reducing in this way until a single-digit
number is produced. This is only applicable to the natural numbers.

Here's how it works:

digital_root(16)
=> 1 + 6
=> 7

digital_root(942)
=> 9 + 4 + 2
=> 15 ...
=> 1 + 5
=> 6

digital_root(132189)
=> 1 + 3 + 2 + 1 + 8 + 9
=> 24 ...
=> 2 + 4
=> 6

digital_root(493193)
=> 4 + 9 + 3 + 1 + 9 + 3
=> 29 ...
=> 2 + 9
=> 11 ...
=> 1 + 1
=> 2

*/