Factorial Calculator (Iterative vs Recursion)

nFactorial.js

// The for loop performs much faster
function nFactorial (num) {
  let factorial = 1;
  for (let i = 1; i <= num; i++) {
    factorial *= i;
  }
  return factorial;
}

// Recursion is about 11× slower
const nFactorial = n => n < 0 ? -1 : n === 0 ? 1 : n * nFactorial(n - 1);