add another way to calculate factorial

snippets/factorial.md

@@ -1,6 +1,12 @@
 ### Factorial
 
-Create an array of length `n+1`, use `reduce()` to get the product of every value in the given range, utilizing the index of each element.
+Use recursion. If `n` is less than (for safety) or equal to `1`, return `1`. Otherwise, return the product of `n` and the factorial of `n - 1`.
+
+```js
+const factorial = n => n <= 1 ? 1 : n * factorial(n - 1)
+```
+
+Another way: create an array of length `n+1`, use `reduce()` to get the product of every value in the given range, utilizing the index of each element.
 
 ```js
 var factorial = n =>