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

You are not returning the return value of isEven(num-2).

Felix Kling
– Felix Kling

2020-02-20 13:11:31 +00:00
Commented Feb 20, 2020 at 13:11 — Felix Kling
– Felix Kling, Commented Feb 20, 2020 at 13:11

mbojko · Accepted Answer · 2020-02-20 13:11:27Z

3

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);

answered Feb 20, 2020 at 13:11

mbojko

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1 Comment

Scott Sauyet Over a year ago

@phortela1n: Don't worry; it's a very common mistake. There are many, many questions in the "recursion" tag with that same issue.

Jeremy Harris · Accepted Answer · 2020-02-20 13:11:37Z

1

You are not returning a value.

Change:

isEven(num-2);

To:

return isEven(num-2);

answered Feb 20, 2020 at 13:11

Jeremy Harris

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1 Comment

phortela1n Over a year ago

Thanks you Jeremy : )

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