Task

Write a boolean function that tells whether a given integer is prime.



Remember that   1   and all non-positive numbers are not prime.

Use trial division.

Even numbers greater than   2   may be eliminated right away.

A loop from   3   to   √ n    will suffice,   but other loops are allowed.



Related tasks

   count in factors
   prime decomposition
   AKS test for primes
   factors of an integer
   Sieve of Eratosthenes
   factors of a Mersenne number
   trial factoring of a Mersenne number
   partition an integer X into N primes
   sequence of primes by Trial Division


function isPrime(n) {
  if (n == 2 || n == 3 || n == 5 || n == 7) {
    return true;
  } else if ((n < 2) || (n % 2 == 0)) {
    return false;
  } else {
    for (var i = 3; i <= Math.sqrt(n); i += 2) {
      if (n % i == 0)
        return false;
    }
    return true;
  }
}