How to detect whether the current line is empty line?

Question

I want a command mapping to detect whether the current line is blank, and perform a different action for each case it detects: true of false. How do I do this?

Answer 1

It is not entirely clear when you say to "trigger some mapping"... Do you want to create a mapping with nnoremap if current line is empty? I guess not. Or you want to have a mapping that does different things depending on whether current line is empty?

If so then there are many possibilities, for example:

func! DoSmth()
    if getline('.') =~ '^\s*$'
        echo 'Do something if empty line!'
    else
        echo 'Do something if NOT empty line!'
    endif
endfunc

nnoremap <space>a :call DoSmth()<CR>