[CodeWars] javascript - 6kyu - Sum of Digits / Digital Root 문제풀이

Title Sum of Digits / Digital Root Description 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_.....