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articles/snippets/javascript-recursion.md

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+---
+title: What is recursion and when is it useful?
+shortTitle: Recursion introduction
+type: question
+tags: [javascript,function,recursion]
+author: chalarangelo
+cover: curve
+excerpt: Recursion is a very important programming concept all developers should be familiar with.
+dateModified: 2022-01-23T05:00:00-04:00
+---
+
+Recursion is the **repeated application of a process**. In JavaScript, recursion involves functions that call themselves repeatedly until they reach a base case. The base case breaks out of the recursion loop, thus allowing previous calls to the function to return a result. If no such case exists, the function will call itself indefinitely resulting in a stack overflow.
+
+Recursion is used to solve problems where the solution depends on solutions to smaller instances of the same problem. A commonly-used example of a problem that can be solved recursively is the Fibonacci sequence:
+
+```js
+const fibonacci = n => {
+  if (n <= 1) return n;
+  return fibonacci(n - 1) + fibonacci(n - 2);
+};
+
+fibonacci(6); // 8
+```
+
+The base case for this example is `n` being less than or equal to `1`, where the function returns the value of `n`. Any other value will call the `fibonacci` function twice to compute the values of `n - 1` and `n - 2`. These will in turn call the `fibonacci` function again until the base case is reached.
+
+While the Fibonacci sequence can be solved with recursion, it can be more efficient to solve it using iteration. However, the inverse is true for a lot of other problems where identifying and indexing the sub-problems is difficult or costly.