Iterative and recursive methods to find if a number is a prime in JavaScript

isPrime.js

function isPrime(num) {
    var count = 2;
    while(count < num) {
     if(num % count == 0) {
        return false;
    }
    count ++;
   }
   return true;
}

function isPrimeRecursive(num, half) {
    if(half === 0 || num === 1) {
        return true;
    }
    half = half || parseInt(num/2);
    if(num % half === 2 && half !== 1) {
        return false;
    } else {
        return isPrime(num, half - 1);
    }
}