JSFiddle - React, Tailwind, and code Playground

by Vladymyr Shevchuk

JavaScript

function addDigits (number) {
  let result = 0;

  const doStep = (number) => {
    const string = `${number}`;

    const sum = string => [...string].reduce((accum, item) => {
      return accum + parseInt(item, 10);
    }, 0);

    if (number < 10) {
      result += number;
    } else {
      result += doStep(sum(string));
    }
  };

  doStep(number);

  return result;
}

console.log(addDigits(44));