Factorial

factorial.js

// Recursively
// From `n`, all the way down to 1
function factorial(n) {
  if (n < 2) {
    return 1;
  }
  
  return n * factorial(n - 1);
}

// Iteratively
// From 1, all the way up to `n`
function factorial(n) {
  let result = 1;
  
  for (let i = 1; i <= n; i++) {
    result *= i;
  }
  
  return result;
}