primes.interview.js

var primeTotal = function(){
  var limit = 2000000;
  var result = 0;
  
  for (var i = 2; i <= limit; i++){
    if (primeTester(i)){
        result += i;
    }
  }
  return result;
}

var primeTester = function(n) {
    
  // n isn't a number or n is less than 1 or n is not an integer    
  if(typeof n !== 'number' || n < 2 || n % 1 !== 0){
    return false;
  }
  
  // if n is 2
  if (n === 2) return true;
  
  // if n is divisible by 2
  if (n%2 === 0) return false;

  var sqrt = Math.ceil(Math.sqrt(n));
  
  for(var i=3; i<=sqrt; i+=2){
    if (n%i === 0) return false
  }
  
  return true;
};

console.log(primeTotal());