out of the box type of thinking, my admiration!

This is super awesome!

Awesome, I wasn't aware that Array.from() takes a map function as the second argument. Will prove very handy in the future 🙏

The original instructions call to return a set of Date types that are sorted chronologically. However, a "set" by definition is a collection of items that are: unordered, unchangeable, and unindexed. Therefore, the program was modified to return a sorted list instead.

Haha, same, good to know :D

still no answer, some kind of magic... :)

It's good coding practice to restrict mutability. As the instance variables are never changed we can make them immutable. Even better: Thus the whole class Dinglemouse becomes immutable - an instance of Dinglemouse can never be changed after initialization. As for the parameters it might not be mandatory to declare them final, but I made it a habit to declare all variables final by default, unless for the rare occasion where I really need a mutable variable. Also it is best avoided to change the value of parameters, so declaring them final makes this more explicit.

Excuse me. why use final in this case?

I think that the description can be misleading insofar as it doesn't explicitly mention what should happen to non-alphabetic characters. Should they degrade at all? If you think of a real-life photocopier, you might assume, that even numbers and special characters can decay over time. This led me to wrongly allowing the whitespace character as a legal successor in the copy to just any original character.

So although the description and the test cases implicitly define the expected behavior, a more explicit hint would be very helpful. I suggest an extra bullet point under "Notes" stating that other characters do not degrade, as @docgunthrop already proposed.

I'd like to join in on the praise. A really nice series of katas. Thank you.

Fixed.

I did that way in my python translation. Thanks

really nice!

In my opinion you desctibe 'best practice', but 'clever'.