How to use ARRAYFORMULA with TEXTJOIN?

Question

I have Google Sheet document and I use TEXTJOIN in it. I want to have my TEXTJOIN formula filled when i add new rows. But it doesn't work

So I tried to use ARRAYFORMULA. IT works with numbers:

But it still doesn't work with TEXTJOIN:

Any Ideas?

UPD: If I use & instead of TEXTJOIN it works but in fact i shoud use delimiter and I should avoid double delimiter. I shouldn't have any a--a or d-D-:

Answer 1

Giving multiple array ranges to Arrayformula, and trying to force it to evaluate it in a specific order, is a losing battle. Try something simpler instead:

=arrayformula(A1:A & " " & B1:B)

P.S. Your animated illustrations do show a level of effort on your part to ask a nice question, but frankly my eyes hurt from watching 3 cursors simultaneously, I'd prefer just the formulas or static images.