CODE EXAMPLE FOR JAVASCRIPT

prime number in javascript using for loop

function sumPrimes(num) {
  // Prime number sieve
  let isPrime = Array(num + 1).fill(true);
  // 0 and 1 are not prime
  isPrime[0] = false;
  isPrime[1] = false;
  for (let i = 2; i <= Math.sqrt(num); i++) {
    if (isPrime[i]) {
      // i has not been marked false -- it is prime
      for (let j = i * i; j <= num; j += i)
        isPrime[j] = false;
    }
  }

  // Sum all values still marked prime
  return isPrime.reduce(
    (sum, prime, index) => prime ? sum + index : sum, 0
  );
}