From fetching data to fighting with imperative APIs, side effects are one of the biggest sources of frustration in web app development. And let’s be honest, putting everything in useEffect hooks doesn’t help much. Thankfully, there is a science (well, math) to side effects, formalized in state machines and statecharts, that can help us visually model and understand how to declaratively orchestrate effects, no matter how complex they get. In this talk, we’ll ditch the useEffect hook and discover how these computer science principles can be used to simplify effects in our React apps.