Nice one indeed, i actualy did the smae as you.

wow

Can you explain what "array size extension" is exactly? I'm looking at your answer and see "fill" and "concat". Would these not be considered array size extensions also? Is your answer the best answer? If so, is filling a new array and concat better than push and spreading? How come?

yes that solution is not be best because of unnecesary loops.
but yours has unnecessary array size extension (pushs) too. same with array destructuring

slow

This is exactly what I did and I was wondering about this - thanks!

2 loops unnecessarily is not best practice.

Hi there

The main problem here is that Codewars does not indicate which JavaScript version the katas and solutions target.

There is also no indication how old this kata and the solutions are, in fact they are from a time when fat arrows and other modern constructs were not yet available in JavaScript.

Another problem is that there is no indication whether the solution should be optimized for speed or for readability.

If the lists are very small and the function is not used frequently, a simple and readable solution might be preferred over an optimized and faster one.

Please use spoiler flag next time. Your post was visible in the homepage.

Quite readable? The lack of any new lines and multiple returns on one lie is poor form. I wouldn't approve code like this in merge requests.

you're 4 kyu so a 30 minute problem can either be 5kyu or 6 kyu easily so it's not outrageous. And if it's not outrageous no need to cherry pick