Factorial of a number

Examples

Example 1

Input: n = 0
Output: 1

• Explanation: 0! = 1 by definition.

Example 2

Input: n = 4
Output: 24

• Explanation: 4! = 4 × 3 × 2 × 1 = 24

Example 3

Input: n = 6
Output: 720

• Explanation: 6! = 6 × 5 × 4 × 3 × 2 × 1

Constraints

• n must be a non-negative integer
• Large values of n may cause recursion depth issues
• Return false for negative numbers
• Return false for non-integers
• Return false for non-numeric values (NaN, strings, arrays, objects, null, undefined)

Function Signature

function factorial(n) { }

Test Cases

n	Expected Output
0	1
1	1
3	6
5	120
7	5040
10	3628800
Invalid inputs → false Examples:

• factorial(-1)
• factorial(2.5)
• factorial("5")
• factorial({})
• factorial([])
• factorial(null)
• factorial(undefined)