Factorial of a number

Problem Statement

Solution 1: Recursive Approach

function factorialRecursive(number) {
    if (number < 0) {
        throw new Error("Factorial cannot be calculated for negative values.");
    }
    if (number === 0 || number === 1) {
        return 1;
    }
    return number * factorialRecursive(number - 1);
} 

const n1 = 5;
factorialRecursive(n1);  //output: 120 

const n2 = 22;
factorialRecursive(n2);  //output: 1124000727777607680000 

Solution 2: Iterative Approach

function factorialIterative(number) {
    if (number < 0) {
        throw new Error("Factorial cannot be calculated for negative values.");
    }
    let product = 1;
    for (let i = 2; i <= number; i++) {
        product *= i;
    }
    return product;
} 

const n1 = 5;
factorialIterative(n1);  //output: 120 

const n2 = 22;
factorialIterative(n2);  //output: 1124000727777607680000 

Solution 3: Tail-Recursive

function factorialTailRecursive(number, accumulator = 1) {
    if (number < 0) {
        throw new Error("Factorial cannot be calculated for negative values.");
    }
    if (number === 0 || number === 1) {
        return accumulator;
    }
    return factorialTailRecursive(number - 1, accumulator * number);
} 

const n1 = 5;
factorialTailRecursive(n1);  //output: 120 

const n2 = 22;
factorialTailRecursive(n2);  //output: 1124000727777607680000 

Solution 4: Using array map reduce

function factorialArrayMapReduce(number) {
  if (number < 0) {
    throw new Error("Factorial cannot be calculated for negative values.");
  }
  return [...Array(number + 1).keys()]
    .slice(1)
    .reduce((product, current) => product * current, 1);
} 

const n1 = 5;
factorialArrayMapReduce(n1);  //output: 120 

const n2 = 22;
factorialArrayMapReduce(n2);  //output: 1124000727777607680000 

Solution 5: Using while loop

function factorialWhileLoop(number) {
    if (number < 0) {
        throw new Error("Factorial cannot be calculated for negative values.");
    }
    let product = 1;
    let i = 2;
    while (i <= number) {
        product *= i;
        i++;
    }
    return product;
} 

const n1 = 5;
factorialWhileLoop(n1);  //output: 120 

const n2 = 22;
factorialWhileLoop(n2);  //output: 1124000727777607680000 

Resources

Frequently asked questions

1. What is factorial?

   See the factorial of a number n, written as n!, is found by multiplying all whole numbers from 1 up to n.

   For example:

   • 5!=5×4×3×2×1=120

   • 3!=3×2×1=6

2. What is the factorial of 5?

   Factorial of 5 is 120. You can run these functions to check.

3. Can we calculate factorial of a negative integer.

   No factorial of a number can not be calculated for negative integers. Only Positive integers

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