Tests if a number is prime using JavaScript/Python. The function isPrime will return 0 if the value passed is prime and it's lowest prime divisor or 1 if it is not.

primes.js

function testDivisors(value, divisor1, divisor2) {
    if ((value != divisor1) && (value % divisor1 === 0)) {
        return divisor1;
    } else if (value != divisor2 && value % divisor2 === 0) {
        return divisor2;
    } else {
        return 0;
    }
}
 
function isPrime(value) {
    var count, divisor, maxN;
    
    if (value > 1) {
        divisor = testDivisors(value, 2, 3),
        maxN = Math.round(Math.sqrt(value) / 6);
 
        for (count = 1; count <= maxN && divisor === 0; count += 1) {
          sixCount = 6 * count;
          divisor = testDivisors(value, sixCount - 1, sixCount + 1);
        }
 
        return divisor;
    } else {
        return 1;
    }
}

primes.py

import math


def testDivisors(value, divisor1, divisor2):
	if value != divisor1 and value % divisor1 == 0:
		return divisor1
	elif value != divisor2 and value % divisor2 == 0:
		return divisor2
	else:
		return 0
 
 
def isPrime(value):
	if value > 1:
		divisor = testDivisors(value, 2, 3)
		maxN = round(math.sqrt(value) / 6)
		count = 1
 
		while (divisor == 0) and (count <= maxN):
			sixCount = 6 * count
			divisor = testDivisors(value, sixCount - 1, sixCount + 1)
			count += 1

		return divisor
	else:
		return 1