Factorial of a number using JavaScript

Given a positive integer n and the task is to find the factorial of that number using JavaScript code.

For any positive integer ‘n’, the factorial of n is the product of all the values from 1 to n. In mathematics, the factorial of n is represented by n!. a factorial of 0 is 1.

Note: Factorials of negative numbers are not defined as only positive numbers including 0 are defined in the domain of factorials.

JavaScript Program for Factorial

Examples:

Input : 4
Output : 24

Input : 5
Output : 120

Table of Content

Iterative Method
Recursive Method

Approach 1: Iterative Method

Declare a variable with a value of the number whose factorial you have to find.
Declare a function factorial taking the value as a parameter.
In the function definition, initialize variable ans to 1.
Loop in the range of [2, n].
Multiply ans by the value of i in each iteration.
Return the value of ans.

Example: In this example, we a following iterative method.

Javascript

let n = 5; 
 
function factorial(n) { 

    let ans = 1; 

    if(n === 0)

        return 1;

    for (let i = 2; i <= n; i++) 

        ans = ans * i; 

    return ans; 
}
 
console.log(factorial(n));

Output

Time Complexity: O(n) Since the code is running for all the values of n

Space Complexity: O(1) As we are not allocating any extra space for a variable.

Approach 2: Recursive Method

Declare a variable with a value of the number whose factorial you have to find.
Declare a recursive function factorial taking the value as a parameter.
The function returns 1 if the value is 0 else the return calls the function for value – 1.
After recursion is over the value returned is the factorial.

Example: In this example, we are following Recursive method

Javascript

let n = 5;

function factorial(n) { 

    if (n === 0) { 

        return 1; 

    } 

    else { 

        return n * factorial( n - 1 ); 

    } 
} 
 
console.log(factorial(n));