What is the problem in this recursive javascript function? [JS]

Question

Hi to all I am trying to make a program in order to output when a number is Even using recursive calls. Can anybody please say me why it doesn't work as I expected?.

const isEven = num => {
  if (num === 0) return true;
  else if (num === 1) return false;
  //console.log(num);
  isEven(num-2);
}

isEven(16); // Epected Log: 0 but instead it returns undefined

Answer 1

Because for arguments different than 0 or 1 there is no return value. The last line:

  isEven(num-2);

should be

  return isEven(num-2);

Answer 2

You are not returning a value.

Change:

isEven(num-2);

To:

return isEven(num-2);