You are assuming the inner function always accept 2 arguments only, no more, no less...

have you used timeit to compare the performance of your Counter() solution with this one? I personally believe that your solution could be 10X slower.

Time complexity is O(n^2), would not consider it as 'best practices' while there are more optimal solutions (e.g. see Counter).

Not a suggestion...?

5 undefined
Test Passed: Value == 25

5 undefined
Cached function did not return the correct result - Expected: 125, instead got: 25

I think it should have expected 25 and not 125, else what is the point of caching in this case ? or am I totally missing something ?

Performance KATA of the same as a suggestion.. thanks for the KATA BTW!

Very nice Kata, though my solution stinks but I learnt a lot, thanks to the author... /

Nevermind... my bad didn't read the instructions carefully.

Passed: 24 Failed: 0 Exit Code: 1
Shows timeout...is there a catch to the Kata that I have missed ?

I like very much ;)

You don't have to compare the value in the filter to true or false and what's most important, you shouldn't use the == for that as that is waaay less performant (read about coercion in JS).

finally some helpful hint :)

Cheers!

Not an issue of the kata. Report it as a bug to CW: https://www.codewars.com/topics/bug-reports