Quicky run an external command (eg node) on current buffer and show output in temporary vertical split

quick-command.vim

" Add the following in your vim config

function! ShowNodeResult()

  " command to run on current buffer
  let op = system("node", bufnr())
 
  " name of output buffer
  let win = bufwinnr("__NODE_OUTPUT__")

  " Check if existing output buffer exists
  if win == -1
    " If not exists, create a new one
    vsplit __NODE_OUTPUT__
    " Do not save to disk or create backups
    setlocal buftype=nofile 
    setlocal nobackup noswapfile nowritebackup
  else
    " If exists, switch to it
    exe win . "wincmd w"
    " Clear buffer
    normal! ggdG
  endif

  " Append output
  call append(0, split(op, '\v\n'))

endfunction

" Bind to a command 
command! -nargs=0 Node :call ShowNodeResult()

" To close the window on exit
augroup nodeOP
  autocmd!
  autocmd BufLeave __NODE_OUTPUT__ bwipe
augroup end

" Inspired by : https://learnvimscriptthehardway.stevelosh.com/chapters/52.html