无法解释的返回值不确定

Question

I've got an issue with an undefined value in below code that neither me nor any of my collegues can explain:

function reverseFactorial(num) {
  function reverse(altNum, fac){
  console.log(altNum + ', ' + fac);
    if ((altNum / fac) === 1)
            {  
            console.log(fac.toString() + '!');
       return fac.toString() + '!'; 
            }

       else {
       reverse(altNum / fac, fac + 1);
       }
  }
  var ret = reverse(num, 1);
  console.log(ret);
  return ret;
}

An example input could be: reverseFactorial(120) .

The logs would then show this:

120, 1

120, 2

60, 3

20, 4

5, 5

5!

undefined

Answer 1

The reverse function doesn't always return a value: the else { case has no return statement.

You probably mean to return reverse(altNum / fac, fac + 1); in the else block.