Remove trailing whitespace automatically in vim

gistfile1.vim

if has("autocmd")
  autocmd BufWritePre {*.rb,*.js,*.coffee,*.scss,*.haml,*.py,*.js} :call <SID>StripTrailingWhitespaces()
endif

nnoremap <silent> <F5> :call <SID>StripTrailingWhitespaces()<CR>

function! <SID>StripTrailingWhitespaces()
    " Preparation: save last search, and cursor position.
    let _s=@/
    let l = line(".")
    let c = col(".")
    " Do the business:
    %s/\s\+$//e
    " Clean up: restore previous search history, and cursor position
    let @/=_s
    call cursor(l, c)
endfunction