Problem-9_Find_the_Factorial_of_a_Number.js

// Problem-9_Find_the_Factorial_of_a_Number with Solution, Explanation, Verification, and Execution:

// To find the factorial of a number, we can implement the Solution like below:
// -------------------------------------------------------------------

function factorial(n) {
    if (n < 0) return null;
    let result = 1;
    for (let i = 1; i <= n; i++) {
        result *= i;
    }
    return result;
}

// Explanation: 
// ---------------
// The function first checks for negative input, returning null as factorial is undefined for negatives. It initializes the result to 1 (factorial of 0 or 1). A for loop multiplies the result by each integer from 1 to n inclusive. This iterative multiplication builds the factorial value progressively, using a loop instead of recursion for simplicity and efficiency.

// Verification:
// ----------------

// function factorial(n) {
//     if (n < 0) return null;
//     let result = 1;
//     for (let i = 1; i <= n; i++) {
//         result *= i;
//     }
//     return result;
// }
// console.log(factorial(5));

// Execution of the above code block in IDE environment with node.js installed:
// ----------------------------------------------------------------------
// Input (In the directory in IDE environment with node.js installed): 'node Problem-9_Find_the_Factorial_of_a_Number.js'
// Output (In the directory in IDE environment with node.js installed): "Hello World"