Question

I know these commands in Vim:

J : Join line below after current line
-J : Join current line after line above

but how do I join the line above after current line?

Answer 1

There are many ways to do it. One would be… deleting the line above and appending it to the end of the line below:

k move up one line
^ move to the first printable character
y$ yank to the end of the line
"_d get rid of the now useless line by deleting it into the black hole register
$ move to the end of the line
p put the deleted text