25: Functions and Recursion

In JavaScript you have the ability to do something called "recursion", but it's not a very safe thing to do. Recursion is where a function calls itself, and by doing that creates a loop. In JavaScript this causes a new function call, which means if you do it too much you run out of memory and cause a crash. However, if you are going to learn about "functional programming" you need to know how recursion works.

Consider this exercise a novelty that you shouldn't really use.

The Code

Recursion is very simple but many beginners get confused that it actually works. To them it seems odd that a function can call itself. There's nothing odd about it because you can usually combine features of a language, and calling a function is one of those features. Once you realize that this is possible you can create very complicated ways of looping that do not need for-of or while-loop style of processing.

In this code I simply loop over a range of numbers using recursion, and then do a more complex version that uses a callback.