Sum Prime Non Prime - Nested Loops

function sumPrimeNonPrime(input) {
    let index = 0;
    let primeNums = 0;
    let nonPrimeNums = 0;

    while (input[index] !== 'stop') {
        let num = Number(input[index]);

        if (num < 0) {
            console.log(`Number is negative.`);
        } else {
            let isPrime = true;
            for (let i = 2; i < num; i++) {

                if (num % i == 0) {
                    isPrime = false;
                    break;
                }
            }

            if (isPrime) {
                primeNums += num;
            } else {
                nonPrimeNums += num;
            }
        }
        index++;
    }

    console.log(`Sum of all prime numbers is: ${primeNums}`);
    console.log(`Sum of all non prime numbers is: ${nonPrimeNums}`);

}

sumPrimeNonPrime(["3", "9", "0", "7", "19", "4", "stop"])