Function factorial

factorial(n: number): number
Calculates the factorial of a non-negative integer n.

The factorial of a number n is the product of all positive integers less than or equal to n.
Parameters
- n: number
  A non-negative integer.
Returns number
The factorial of n.
Throws
Will throw an error if n is negative or not an integer.
Example
```
factorial(0); // returns 1
factorial(5); // returns 120
factorial(3); // returns 6
```
- Defined in factorial/factorial.ts:17