factorial.js

/*
In mathematics, the factorial of a non-negative integer n, denoted by n!, is the product of all positive integers less than or equal to n. For example: 5! = 5 * 4 * 3 * 2 * 1 = 120. By convention the value of 0! is 1.

Write a function to calculate factorial for a given input. If input is below 0 or above 12 throw an exception of type ArgumentOutOfRangeException (C#) or IllegalArgumentException (Java) or RangeException (PHP) or throw a RangeError (JavaScript) or ValueError (Python) or return -1 (C).

More details about factorial can be found here.
*/

//ANSWER//

function factorial(n) {
  if (n < 0 || n > 12)
    throw new RangeError();
  return n <= 1 ? 1 : n * factorial(n - 1);
}

//OR//

function factorial(n){
if (n === 0 || n === 1)
    return 1;
if(n<0||n>12){throw RangeError
}
  for (var i = n - 1; i >= 1; i--) {
    n *= i;
  }
  return n;
}