in my .vimrc i have an autocmd which cleans up my files, but how can i make a mapping out of the command?
autocmd BufWritePre *.test1 silent! :%s/\s\+$//e | silent! :%s/\(\n\n\)\n\+/\1/ | silent! :%s#\($\n\s*\)\+\%$## | :%s/;$
nnoremap ;; silent! :%s/\s\+$//e | silent! :%s/\(\n\n\)\n\+/\1/ | silent! :%s#\($\n\s*\)\+\%$## | :%s/;$<CR>
The mapping fails saying
Error detected while processing ~/.vimrc:
line 966:
E486: Pattern not found: ;$<CR>
So the main problem with your command is that by using | you're actually breaking it into several commands, the first of which being nnoremap, but from the second on, a series of silent! commands with substitutions, which are being run at the time your .vimrc is being sourced, rather than becoming part of the command.
Using either \| or <bar> should solve that.
The second issue is that nnoremap expects a command in normal mode, so it takes your silent! and runs the s (substitute) command, which then replaces the character under the cursor with ilent! ..., which is not what you want... You need an extra : before that first silent! so it knows to go into command mode.
And third, your last command %s/;$<CR> is not really well formed, you need two additional /s to complete it. I'm assuming your intention is to strip all ;s at the end of lines, so %s/;$// is what I'm assuming you want here. (I also noticed you skipped a silent! there, maybe by omission? I'm adding it here, just in case.)
Putting it all together:
nnoremap ;; :silent! :%s/\s\+$//e \| silent! :%s/\(\n\n\)\n\+/\1/ \| silent! :%s#\($\n\s*\)\+\%$## \| silent! :%s/;$//<CR>
