Vimrc syntax move up and down a certain line continously

Question

So I am new to Vim and I am trying to understand the language of vimrc. I have this in my vimrc:

map <F8> <C-E>: sleep 100m<CR>j<F8>

This would automatically move the cursor down when I press F8. However, what if I want the cursor to move down 1 line then move up 1 line, then down 1 line again and repeat? It's a dumb question I know, but I try to understand how the language vimscript works. Anyway, I try this:

map <F8> <C-E>: sleep 100m<CR>1j1k<F8>

That only scolls downward, not upward. I want it to move down 1 line, then up 1 line then repeat until I press Ctrl-C to cancel.

Pleast let me know your help

Answer 1

You'd need to include the whole sequence, including the opposite of <C-E>, which is <C-Y>, and also the :sleep.

map <F8> <C-E>:sleep 100m<CR>j<C-Y>:sleep 100m<CR>k<F8>