a accumulates the array item values by adding them. That's the first +. The second + converts the array item b from a string into a number so it can be added to the accumulator a.

No it doesn't. It returns the correct output, ie ['', 0]

It stands for temporary.

Great solution.

I have reworded the description a bit for more clarity.
A couple of things:

• unless you really want to give away a strong hint on how to solve this kata, I would remove the below altogether:
  
  (You need to find two characters that are equally spaced from the ends of the string that are different. And vozvernut the number of that letters, by removing which we get the palindrome).
  

Great Kata, it really helped me better understand how to use and structure classes in Javascript. So thank you.

You need to use opening and closing quotation marks between the parentheses. So word.split('') or word.split("").

Nice clean solution.

You don't. It was an oversight.

Good job.

Really clever solution. Well done.

Great kata. Quite hard though. 6kyu in my opinion.

Great Kata! Looking at the kata stats though, it looks like the average rating was 6kyu, so I am just wondering why it is only a 7kyu? (It certainly felt like a 6kyu to me! (Javascript)).

Superb solution.