Prime Number checker

A simple Prime number checker in JS code

function isPrime(num) {
    if (num <= 1) return "no";
    if (num <= 3) return "yes";
    if (num % 2 === 0 || num % 3 === 0) return "no";
    
    for (let i = 5; i * i <= num; i += 6) {
        if (num % i === 0 || num % (i + 2) === 0) return "no";
    }
    
    return "yes";
}

const number = 13; // you can change the number if you like
console.log(isPrime(number)); // Output should be: yes