JSFiddle - React, Tailwind, and code Playground

by AlexGun

JavaScript

function digital_root(n) {
  let currentResult = n
  let length = n.toString().length
	while (length > 1) {
    n.toString().split('').forEach(item => currentResult += +item) 
    length = currentResult.toString().length
   }
   
   return currentResult
}

console.log(digital_root(132189))