There's a way to make it one line tho :)
One line solutions are usually not the best ones (in terms of performance and readability) but people still upvote them because they look cool

That's true. But then I'd have to do -1 in 3 places. And my two < would become <=.

Nice solution, could start your iterators at 1 to avoid the + 1

Assigning is slightly faster than pushing (~20%). Either way is fine though.

What's better? doing push() or assign a value to a nonexistent element of the array?

Being a new JS Programmer, I was becoming disillusioned with every "easy" Kata top solution being one line of Regex.
I'm happy to finally see something very close to my answer as Best Practice.