# Sum of all prime numbers in JavaScript

JavascriptWeb DevelopmentFront End TechnologyObject Oriented Programming

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We are required to write a JavaScript function that takes in a number as the only argument. The function should find and return the sum of all the prime numbers that are smaller than n.

For example −

If n = 10, then the output should be 17, because the prime numbers upto 10 are 2, 3, 5, 7, whose sum is 17

## Example

The code for this will be −

const isPrime = (num) => {
let x = Math.floor(Math.sqrt(num));
let j = x;
while (j >= 2) {
if (num % j === 0) {
return false;
}
j−−;
}
return true;
};
const sumOfPrimes = (num = 10) => {
let iter = num;
let sum = 0;
while (iter >= 2) {
if (isPrime(iter) === true) {
sum += iter;
}
iter−−;
}
return sum;
};
console.log(sumOfPrimes(14));
console.log(sumOfPrimes(10));

## Output

And the output in the console will be −

41
17
1060