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 factorial of n is represented by n!. 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

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:

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

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

As we are not allocating any extra space for a variable so the Auxiliary Space: O(1):

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:

Javascript

let n = 5;
function factorial(n) { 
    if (n === 0) { 
        return 1; 
    } 
    else { 
        return n * factorial( n - 1 ); 
    } 
} 
  
console.log(factorial(n));