Fixed and random cases with symbol characters are now tested. Closing.

yes, but in JS it is definitely harder now than in Python.

Good solution! It could use a little refactoring, but other than that - it's concise but not concise to the point of unintelligible.

Yes

This does not work correctly for negative numbers.

Standard Math object: Math.floor(-1.1) === -2

This implementation: Math.floor(-1.1) === -1

You are correct. I made mistakes. Just fixed them.
They did not change results. So no one noticed.
Thank you very much!

If my testcode run correctly there should not be things like ABA. I modified the testcode from another kata I made which may have certain disconnected cases. Maybe I missed something. Did you see this type of disconnected areas in the tests?

Thank you so much for pointing out the typo. I corrected it.

If there are two disconnected areas with the same letter, are they considered one territory or two distinct territories?
Consider for example the string ABA. Do the two As form two separate territories or one discontinuous territory?

Also please note that there is a typo in the description. "chese board" > "chessboard".

Not an issue, but a suggestion. Anyway, I removed that test, as there were other complaints earlier about it.

Yup, you got it right o_O

I created a fork with verbose comments to explain what is going on in this solution.
I hope I got it right...

Your clever solutions are a bit difficult to read... :-)
I created a fork of your solution with unnecessarily verbose comments to explain it to other warriors.
I hope I got the comments right.

Sorry for spamming by posting the same solution three times with only very little changes. (I just updated a misleading name of a variable here.)
I wanted to delete my previous submissions but it does not seem to be possible.