javascript algorithms and data structures interview questions

function isPrime(n)
{
  var divisor = 3, 
      limit = Math.sqrt(n);
  
  //check simple cases
  if (n == 2 || n == 3)
     return true;
  if (n % 2 == 0)
     return false;

  while (divisor <= limit)
  {
    if (n % divisor == 0)
      return false;
    else
      divisor += 2;
  }
  return true;
}

> isPrime(137);
  = true
> isPrime(237);
  = false