Recursion is a key concept in coding. Gavin explains it simply here.

[00:00] So, what is recursion? Think of it like [00:02] standing between two mirrors. You see [00:05] the image repeating smaller and smaller [00:07] each time. Recursion is when a function [00:10] calls itself potentially several times [00:12] to solve a problem. Let's look at a [00:14] basic practical code example in [00:16] JavaScript where recursion is used to [00:19] solve a problem. In this case, the [00:21] problem is calculating [00:23] factorials. [00:25] So, what is a factorial? A factorial is [00:27] a way of multiplying a whole number by [00:30] all the positive integers below it. [00:33] So, what is the factorial of three? [00:36] We can calculate the result like this: 3 [00:39] * 2 * 1, which equals to 6. The [00:41] factorial of 3 is 6. What is the [00:44] factorial of 5? We can calculate the [00:46] result like this: 5 * 4 * 3 * 2 * 1, [00:51] which equals 120. The factorial of 5 is [00:54] 120. You can see that this pattern of [00:56] logic is repeating until the final [00:58] multiplication operation involves [01:00] multiplication by the value of 1. This [01:02] alludes to the base case. And when the [01:05] base case is true, the pattern of logic [01:07] needs to stop repeating. So, this is [01:10] where the final result is calculated, [01:12] and we no longer want to continue [01:14] calling the recursive function. So, the [01:16] recursive reusable function to calculate [01:18] factorials looks like this. The function [01:21] calls itself until the base case is [01:23] true, i.e., when n equals to 1. [01:26] The final result is returned after the [01:28] result is multiplied by 1. So, the [01:30] function keeps calling itself until it [01:33] hits a base case, the stopping point. [01:36] Remember, no base case equals to [01:38] infinite loop. [01:40] So, that's recursion, breaking big [01:42] problems into smaller versions of [01:45] themselves.