function sumPrimes(num) {

  var arr = [];
  var sum = 0;

  for(var i = 2; i <= num; i++){
    arr.push(i);
  }


   for(var j in arr){

     for(var k = 2; k < num; k + k++){

       if(arr[j] !== k && arr[j] % k === 0){
         arr[j] = 0;
       break;
       }

     }

      sum+=arr[j];
  }


  return sum;
}

sumPrimes(977);