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Sum of All Primes

Sum of All Primes

Sum of All Primes

function sumPrimes(num) {
// Helper function to check primality
function isPrime(num) {
for (let i = 2; i <= Math.sqrt(num); i++) {
if (num % i == 0)
return false;
return true;

// Check all numbers for primality
let sum = 0;
for (let i = 2; i <= num; i++) {
if (isPrime(i))
sum += i;
return sum;


can someone explain me please how is 2 added to sum, since 10 is divisible with 2 and after executing this line if (num % i == 0)
return false; is returning false?and is IsPrime si false 2 is not added to sum...

And how 4 and 5 and the rest of the numbers are checked if the for (let i = 2; i <= Math.sqrt(num); i++) Math.sqrt(10) is 3,16?
it means that is only checking 2 and 3...?

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