Sum of prime numbers between a range - JavaScript

We are required to write a JavaScript function that takes in two numbers, say a and b and returns the sum of all the prime numbers that fall between a and b. We should include a and b if they are prime as well.

Example

Following is the code −

const num1 = 45;
const num2 = 345;
const isPrime = n => {
   if (n===1){
      return false;
   }else if(n === 2){
      return true;
   }else{
      for(let x = 2; x < n; x++){
         if(n % x === 0){
            return false;
         }
      }
      return true;
   };
};
const primeBetween = (a, b) => {
   const res = [];
   while(a <= b){
      if(isPrime(a)){
         res.push(a);
      };
      a++;
   };
   return res;
};
console.log(primeBetween(num1, num2));

Output

Following is the output in the console −

[
    47,  53,  59,  61,  67,  71,  73,  79,  83,
    89,  97, 101, 103, 107, 109, 113, 127, 131,
   137, 139, 149, 151, 157, 163, 167, 173, 179,
   181, 191, 193, 197, 199, 211, 223, 227, 229,
   233, 239, 241, 251, 257, 263, 269, 271, 277,
   281, 283, 293, 307, 311, 313, 317, 331, 337
]