JavaScript Program to Find Factorial of a Number

What is Factorial?

Factorial of a positive number n is defined by product of all the numbers starting from 1 to n (both inclusive).

Syntax

n! = n*(n-1)*(n-2)*…1

Factorial of 0 is 1.

Factorial of a negative number cannot be defined.

There are 2 ways to calculate factorial of a number.

Iteration

In this approach, we iterate through all the element from 1 to n and accumulate the product of element.

Syntax

n! = n*(n-1)*(n-2)*…1

Example

function factorial(n) {
  if (n < 0) {
    console.error('invalid number')
    return;
  }
  let result = 1;
  for (let i = 1; i <= n; i++) {
    result = result * i;
  }
  return result;
}

console.log(factorial(6))

Output

720

Using Recursion

In this approach we multiply the number with factorial of that number reduced by 1.

Syntax

n! = n*(n-1)!

Example

function factorial(n) {
  if (n < 0) {
    console.error('invalid number')
    return;
  }
  if (n === 1) {
    return 1
  }
  return n * factorial(n - 1);
}

console.log(factorial(6))

Output

720