The async vs defer breakdown is one of those things experienced devs still get wrong. Really glad you covered it in Day 01 rather than burying it later.

One thing that tripped me up early on: the difference between how defer guarantees execution order (scripts run in document order) while async doesn't. That matters a lot when you have a utility library loaded before your app script. Would be great if a later day covers that execution ordering in depth.

Following the 40 Days series — love the structured approach!