What is recursion in JavaScript?

Overview

In this shot, we learn what is recursion and how to implement it in JavaScript.

Recursion is the process of calling itself until something stops the process. In programming, a function is said to be recursive if it calls itself until something stops it.

Recursion allows us to accomplish what loops (for/while) do. Sometimes, the recursion approach is more elegant than using loops.

Syntax

function recurse() {
    // function code
    recurse()
}
recurse()

Note: The recurse() function calls itself inside the function (Line 3).

How recursion works in JS

Note: When using a recursive function, make sure you have a stop condition (base case) to avoid the function calling itself forever and crashing your browser. This is known as infinite recursion.

Example

In order to see how recursion works, let's write a function that will be counting down from N to 1.

function countDownFrom(number) {
    // print the number
    console.log(number)
    // call the function itself with number - 1
    countDownFrom(number - 1)
}
// call the function
countDownFrom(6)

The code above looks fine, but there's an issue. However, the function is missing the stop condition. This is a typical example of infinite recursion. Let's fix the issue.

function countDownFrom(number) {
    // base case
    if(number == 0) return
    
    // print the number
    console.log(number)
    // call the function itself with number - 1
    countDownFrom(number - 1)
}
// call the function
countDownFrom(6)

Here, we add the base case just at the beginning of the function body (line 3). If the number is 0, end the function execution.

That's all for today. Happy coding!

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