factorial javascript

function factorial(n) {
  if (n < 0) return;
  if (n < 2) return 1;
  return n * factorial(n - 1);
}function factorialize(num) {
  if (num === 0 || num === 1)
    return 1;
  for (var i = num - 1; i >= 1; i--) {
    num *= i;
  }
  return num;
}
factorialize(5);// Simple arrow function solution
var factorial = n => (n <= 0) ? 1: n * factorial(n - 1);function factorialize(num) {
  var result = num;
  if (num === 0 || num === 1) 
    return 1; 
  while (num > 1) { 
    num--;
    result *= num;
  }
  return result;
}