Factorial

FirstFactorial.js

/**
Challenge
Factorial

Sample Test Cases

Input: 1
Output: 1

Input: 4
Output: 24

Input: 9
Output: 362880
*/

function FirstFactorial(num) { 
    if (num === 0) {
        return 1;
    } else {
        return num * FirstFactorial(num - 1);
    }
}

// ES6
firstFactorial = num => {
    return num === 0 ? 1 : num * firstFactorial(num -1);
}