How to define empty REQUEST_URI?

Question

htaccess

The bottom line is:
1) There is a website. Let's say example.com
2) You can access the main page in two versions: example.com and example.com/ (slash at the end)
3) You need to redirect from example.com to example.com/.
4) Actually the question is how to do this using htaccess and is it even possible? As I understand it, request_uri cannot be empty, so in both cases it is equal to a slash (/)

Answer 1

# remove trailing slash
RewriteRule ^(.*)/$ /$1 [L,R=301]
# add trailing slash
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^.*[^/]$ /$0/ [L, R=301]