Today we’re going to revisit a topic we’ve talked about in the past: side effects. We introduced the topic in our second episode with a deep dive on how side effects are kind of like hidden inputs and outputs to our functions, demonstrating how they make testing difficult and how they can introduce subtle bugs. Side effects are complicated and require attention.

The examples in that episode were a bit contrived, so today we’re going to look at code that’s a bit more real-world and explore how we can extract and control side effects quickly and painlessly.

This is a method we’ve used in production again and again, and it’s proven itself over time. We hope that others get the same benefit!