Recursion is a powerful programming technique that allows you to break down a complex problem into simpler sub-problems. It is a process in which a function calls itself directly or indirectly. In JavaScript, recursion is used to solve problems that require the repetition of a set of steps.

- Recursion can be used to solve complex problems that would otherwise be difficult to solve.
- It can simplify code by breaking down a problem into smaller, simpler parts.
- It can be used to create elegant and efficient solutions.

Recursion is a programming technique that allows a function to call itself. It is a powerful tool that can be used to solve complex problems, but it can also be difficult to understand and implement correctly.

In programming, a recursive function is a function that calls itself, either directly or indirectly. This can be used to solve complex problems by breaking them down into smaller, simpler parts. For example, if you wanted to calculate the factorial of a number, you could use a recursive function to do so.

To understand recursion, it is important to understand the concept of a base case. A base case is the simplest possible version of a problem. It is used to stop the recursive process from running indefinitely. In the example of calculating a factorial, the base case would be when the number is 1.

To write a recursive function, you must first define the base case, then write the recursive part. In the case of calculating a factorial, the base case is when the number is 1, and the recursive part is when the number is greater than 1.

index.js

```
function factorial(n) {
// Base case
if (n === 1) {
return 1;
}
// Recursive case
else {
return n * factorial(n - 1);
}
}
```

In the example above, the base case is when the number is 1, and the recursive part is when the number is greater than 1. The function calls itself with a number that is one less than the original number, and the result is multiplied by the original number. This will continue until the base case is reached, at which point the result is returned.

Recursion can be used to solve many complex problems, such as finding the nth Fibonacci number or traversing a tree structure. It can also be used to simplify code by breaking down a complex problem into simpler parts. However, it is important to remember that recursion can be difficult to understand and implement correctly, so it should be used with caution.

index.js

```
function fibonacci(n) {
// Base case
if (n === 0 || n === 1) {
return n;
}
// Recursive case
else {
return fibonacci(n - 1) + fibonacci(n - 2);
}
}
```

1