Calculate the factorial of a number

const factorial = (n) => (n <= 1 ? 1 : n * factorial(n - 1));

const factorial = (n: number): number => (n <= 1 ? 1 : n * factorial(n - 1));

factorial(2); // 2
factorial(3); // 6
factorial(4); // 24
factorial(5); // 120
factorial(6); // 720