This has been resolved some time ago, closing

Ohh, ok. sorry, and thank you for alerting me

Use spoiler flag next time please.

good update with !![] to get 1s, but template literal really looks like cheating

still good improvement

Shortened previous kata with template literals, and true/false Arrays converted into 1's & 0's

The left side of the comparison determines if the variable is NOT an "existing"true or an "integer""not a decimal", the result is undefined

If the left of the comparison fails, then we move to the right comparison

If the integer is odd then return false, else return true.

Because this is kumite. Here it's about showing off skills related to the knowledge of tricks to reduce the length of the code as much as possible, I think. Of course, in "normal" code readability is very important.

Why you dont return simple undefined instead od {}.a ?

I mean:
isEven=n=> n%1==0 ? !(n%2) : undefined

and this is more readability. When you put some whitespace beetween

0

Well done! I didn't know the trick {}.a for undefined...

what does - - do in that code

--str.split(/[aeiou]/i)

Very fun kata to do, especially the "aha" moment upon finding the REDACTED and easily solving it. Thanks for sharing.
Though I must admit the description's Quetzals, Meticals, Zlotys, and Ringglets were of no relevance to the solution, which threw people off.

this solution doesn't work for this case
returnAscending(1,2,3,10,50)
// '11023450'

It's using zero width characters as variable names: Hangul Choseong Filler and Hangul Jungseong Filler