JAVASCRIPT

Javascript prime number check

// 6k+-1 optimisation
function is_prime (n) {
  if (n < 3) return n > 1;
  else if (n % 2 === 0 || n % 3 === 0) return false;
  else if (n < 25) return true;
  let i = 5;
  while (i * i <= n ) {
    if (n % i === 0 || n % (i + 2) === 0) return false;
    i += 6;
  }
  return true;
}

javascript prime number checker program

function prime_checker(num){
    let is_prime;
    if (num===1){is_prime = false}
    else if (num===2||num===3){is_prime = true}
    else if (num%2===0){is_prime = false}
    else{
        let x = Math.floor(num/2);
        while (x>1){
            if (num%x===0){
                is_prime = false;
                break;
            }
            x = x-1;
            is_prime = true;
        }
    }
    
    return is_prime
}