by using slice method, the function can be faster. because in your solution, every loop from filter is start from 0 to end

There seems to be some sort of pattern going on if you examine enough of the results, but the only concrete pattern I could see is that 'n' has to be a multiple of 3 (which can improve the current best solution efficiency).

If the last 2 digits of k are 05|21|26|42|47|63|68|84|89 then n = 9.

39|76 : n = 18.

54|61|75|82 : n = 27.

43|64 : n = 36.

69 : n = 45.

32 : n = 54.

This solutions efficiency can be improved by making the 'n' increment by a step of 3 - the final value of n will always be a multiple of 3.

Clear and concise

Ah yes! Thank you.

IIFE

The string comparison is comparing the first digit, and 5 is greater than 1, so it terminates the comparison. If they were equal it would proceed to the next digit.

I thought solutions (and therefore comments on them) were only visible to those who had completed the kata anyway?

Please use spoiler flag next time.

Can you explain what the concept/s of the syntax is here please? Is it anonymous arrow functions and currying? I understand what's going on with the second line being utilized in the first, just not how the two lines are connected together as (...)(...). Thanks.