Factorial Using Recursion in DSA Typescript - Build from Scratch

Factorial Using Recursion

📖 Scenario: Imagine you are helping a friend who wants to calculate the factorial of a number. Factorial means multiplying a number by all the numbers below it down to 1. For example, 4 factorial is 4 x 3 x 2 x 1 = 24.

🎯 Goal: You will write a small program in TypeScript that uses a function calling itself (recursion) to find the factorial of a number.

📋 What You'll Learn

Create a variable called num with the value 5

Create a function called factorial that uses recursion to calculate factorial

Call the factorial function with num and store the result in result

Print the value of result

💡 Why This Matters

🌍 Real World

Calculating factorials is useful in math problems, probability, and computer science algorithms.

💼 Career

Understanding recursion helps in solving complex problems and is a common topic in programming interviews.

1

Create the number variable

Create a variable called num and set it to the number 5.

DSA Typescript

# Your code here

Hint

Use const num = 5; to create the number variable.

2

Write the recursive factorial function

Create a function called factorial that takes a parameter n. Use recursion: if n is 1, return 1; otherwise return n * factorial(n - 1).

DSA Typescript

const num = 5;
// Your code here

Hint

Remember, the function calls itself with n - 1 until it reaches 1.

3

Calculate factorial and store result

Call the factorial function with num and store the result in a variable called result.

DSA Typescript

const num = 5;

function factorial(n: number): number {
    if (n === 1) {
        return 1;
    } else {
        return n * factorial(n - 1);
    }
}

// Your code here

Hint

Use const result = factorial(num); to store the factorial.

4

Print the factorial result

Print the value of result using console.log.

DSA Typescript

const num = 5;

function factorial(n: number): number {
    if (n === 1) {
        return 1;
    } else {
        return n * factorial(n - 1);
    }
}

const result = factorial(num);

// Your code here

Hint

Use console.log(result); to print the factorial.