# Recursive Functions

In JavaScript, a recursive function is a function that calls itself in order to solve a problem. Recursion is a powerful concept that can be used to solve complex problems by breaking them down into smaller, more manageable subproblems. This document provides an overview of recursive functions in JavaScript, their syntax, common use cases, and best practices.

## Syntax

A recursive function typically has the following structure:

``````function recursiveFunction(params) {
// Base case: the simplest scenario
if (/* base case condition */) {
// return a value or perform an action
} else {
// Recursive case: call the function with modified parameters
return recursiveFunction(modifiedParams);
}
}
``````

Common Use Cases Recursive functions are often used to solve problems that can be divided into smaller, similar subproblems. Here are some common use cases:

Calculating Factorials:

A recursive function can be used to calculate the factorial of a number.

``````function factorial(n) {
if (n === 0) {
return 1; // Base case
} else {
return n * factorial(n - 1); // Recursive case
}
}

factorial(5); // Returns 120
``````

Fibonacci Sequence: The Fibonacci sequence can be calculated using recursion.

``````function fibonacci(n) {
if (n <= 1) {
return n; // Base cases: F(0) = 0, F(1) = 1
} else {
return fibonacci(n - 1) + fibonacci(n - 2); // Recursive case
}
}

fibonacci(5); // Returns 5
``````

Recursive functions are a valuable tool in JavaScript for solving problems that involve repetitive subtasks. When used correctly, they can lead to elegant and efficient solutions.