how to write a function and output a factorial on javascript code example

Example 1: javascript factorial

function factorial(n) {
  if (n < 0) return;
  if (n < 2) return 1;
  return n * factorial(n - 1);
}

Example 2: factorial javascript

num = 5
factorialn = 1
function factorial() {
    for (i = 1; i <= num; i++) {
        factorialn *= i
    }
}
factorial()
console.log(factorialn)