Understanding the exact properties that disqualify a data type from being an instance of a given abstraction turns out to be surprisingly helpful

Abstractions such as functor, monads... are often explained by example, which I think is only half of what's needed to build a solid intuition. The other half is counter-examples: things that *aren't* things. This talk intends to fill that void, by going through the list of common abstractions and showing types that are, say, a functor, but not an applicative. While this may sound more like a toy than something useful, understanding the exact properties that disqualify a data type from being an instance of a given abstraction turns out to be surprisingly helpful, and have certainly allowed me to go further in my study of such things.
How to leverage Scala with scala.js to write frontend as functional programmers would do.
Let's go through some most common patterns when it comes to integrating Scala applications with Kafka