30-seconds-of-code/snippets/factorial.md

factorial

Calculates the factorial of a number.

Use recursion. If n is less than or equal to 1, return 1. Otherwise, return the product of n and the factorial of n - 1. Throws an exception if n is a negative number.

const factorial = n =>
  n < 0 ? (() => { throw new TypeError('Negative numbers are not allowed!') })()
  : n <= 1 ? 1 : n * factorial(n - 1);
// factorial(6) -> 720