SimplePrime.js

// Check if given number is prime
const isPrime = number => {
  // Divide number by all numbers from 2 to sqrt(number)
  // If divisible, then its not a prime
  let div;
  for (div = 2; div < Math.sqrt(number); div++)
    if (number % div == 0) {
      console.log(`Looped ${div} times`);
      return false;
    }
  console.log(`Looped ${div} times`);
  return true;
}

// This is a known prime
console.log(isPrime(1299827));
console.log(isPrime(1299827));

/* Output

Looped 1141 times
1299827 is prime: true
Looped 1141 times
1299827 is prime: true

*/