Number prime test in JavaScript

Question

I'm trying to complete the Codewars challenge that asks you to check if a number is a prime number. For whatever reason, my solution doesn't seem to work for the square of odd prime numbers (e.g. 9 returns true instead of false).

function isPrime(num) {    if (num === 2) {     return true;   } else if (num > 1) {     for (var i = 2; i < num; i++) {        if (num % i !== 0) {         return true;       } else if (num === i * i) {         return false       } else {         return false;       }     }   } else {     return false;   }  }  console.log(isPrime(121));

P.s. I included that second else/if statement because I was trying to solve the problem.

Answer 1

Time complexity: O(sqrt(n))

Space complexity: O(1)

const isPrime = num => {     for(let i = 2, s = Math.sqrt(num); i <= s; i++)         if(num % i === 0) return false;      return num > 1; }