1. solving Sum of Digits / Digital Root and facing problem in this case where input is 010 the output comes 8.
   please can anyone explain?

function fun(n) {
  let numString = n.toString().split("");
  let sum = 0;
  for (let i = 0; i < numString.length; i++) {
    sum += parseInt(numString[i]);
  }
  console.log(sum);
  if (sum >= 10) {
    return fun(sum);
  }
  console.log(numString);
  return sum;
}
console.log(fun(010)); // input- 010 and output- 8

Why the output is 8 but it should be 1.