Handling larger inputs with sum all primes algorithm

JavaScript
1

I am stuck in finding the solution for a larger input, like the one mentioned below, can someone please help me with this,

function sumPrimes(num) {
if(num <=1)
return 0;

var sum = 0;

for(var i=2; i<=num ;i++){
if(isPrime(i)){
sum = sum + i;
console.log(sum);
}
}
return sum;
}

function isPrime(num){
for (var i=2 ;i<=Math.floor(Math.sqrt(num)); i++){
if(num % i == 0)
return false;
}
return true;
}
sumPrimes(977);


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**Link to the challenge:**
https://learn.freecodecamp.org/javascript-algorithms-and-data-structures/intermediate-algorithm-scripting/sum-all-primes/
2

Your isPrime function could be made faster by hoisting the condition out of the loop, since it’s re-evaluated on every pass

var max = Math.floor(Math.sqrt(num));
for (var i = 2; i <= max; i++) { 
... etc
3

This is the first properly challenging task, the main thing to change here is your algorithm to get a better time complexity

The problem of generating primes is a very famous one, so I’d recommend looking into well known much more performant solutions to it

My personal go-to when I have some reason to generate primes is the Sieve of Eratosthenes, though there are reasons this one isn’t the best as well (the space complexity unless handled could be a problem for much larger n)

After you’ve understood and implemented that or another algorithm, if you want to optimise it a bit more consider looking up wheel optimization for the sieve