freeCodeCamp Intermediate Algorithm Scripting: Sum All Primes

sumPrimes.js

// Sum all the prime numbers up to and including the provided number.
// A prime number is defined as a number greater than one and having 
// only two divisors, one and itself. For example, 2 is a prime number 
// because it's only divisible by one and two.

// The provided number may not be a prime.


function sumPrimes(num) {
  let ourSum=0; // We start with one, prime for 1

  for (let i=2; i<=num; i++) {
    let prime=true;
    for (let j=2; j<=Math.sqrt(i); j++) {
      if ((i % j) == 0) { 
        prime=false;
        break;
      }
    }
    if (prime) { 
      ourSum+=i;
    }
  }
  return ourSum;
}

sumPrimes(10);  // 17
sumPrimes(977); // 73156