A recursive function is a function that calls itself. This might sound confusing, but it can be a very powerful tool. When you write a recursive function, you need to have a base case and a recursive case. The base case is when the function doesn’t call itself anymore, and the recursive case is when the function does call itself.

## Base case

In other words a base case is when the problem has been reduced to its simplest form and can be solved without recursion. For our factorial example, the base case would be when n = 1 because we know that the factorial of 1 is just 1 (1 x 1).

Once the base case has been reached, the recursive function will start working its way back up, solving each subproblem until it reaches the original problem. In our example, this would mean multiplying 1 by 2 (the result of the previous calculation), then 3, then 4, and so on until we reach our original number (n).

## Why would you use a recursive function?

There are many reasons why you might want to use a recursive function. One reason is that it can be used to solve problems that are too difficult to solve with an iterative approach. Another reason is that it can be used to simplify complex problems. Finally, recursive functions can be used to create more efficient code.

## How do you write a recursive function?

Writing a recursive function can be tricky, but there are some things you can do to make it easier. First, make sure you understand the problem you’re trying to solve. Second, think about what your base case will be and what your recursive case will be. Third, write out your pseudocode before you start coding. This will help you keep track of what your code is supposed to do. Fourth, test your code often! It’s easy to make mistakes when writing recursive functions, so it’s important to test your code as you go.

## What are some examples of recursive functions?

There are many examples of recursive functions in JavaScript (and in other programming languages). Some common examples include factorials, Fibonacci numbers, and quicksort.

Here’s an example of a recursive JavaScript function `factorial`

that returns a factorial of a given number.

```
function factorial(x) {
if (x === 0) {
return 1;
}
return x * factorial(x - 1);
}
```