Discussion on: Solving the Digital Root Algorithm using JavaScript

[Raymond Price]

Cool demo, but that's not actually recursion, that's just iteration. An actual recursive solution, if you wanted to do that for some strange reason, would look more like

function digitalRoot(number) {
   let arr = number.toString().split("");
   let reducer = (a,b) => parseInt(a) + parseInt(b);
   let sum = arr.reduce(reducer)

   if (sum > 9) {
       return digitalRoot(sum);
   } else {
       return sum;
   }
}

Also, sidenote, this function does break on very large numbers. That's not OP's fault, that's because Javascript can't reasonably represent things like 1234567891234567891234567891 as an integer. digitalRoot("1234567891234567891234567891") works just fine, though