RewriteCond for multiple RewriteRules - .htaccess

Question

currently, I have the following .htaccess-file.
RewriteEngine on
RewriteCond %{HTTP_HOST} ^([a-z-]+)\.example\.com$ [NC]
RewriteCond %1 !^(javascript|css|images)$ [NC]
RewriteRule ^ index.php?file=index [NC,L,QSA]
RewriteCond %{HTTP_HOST} ^([a-z-]+)\.example\.com$ [NC]
RewriteCond %1 !^(javascript|css|images)$ [NC]
RewriteRule ^language/?$ index.php?file=language [NC,L,QSA]
RewriteCond %{HTTP_HOST} ^([a-z-]+)\.example\.com$ [NC]
RewriteCond %1 !^(javascript|css|images)$ [NC]
RewriteRule ^about-us/?$ index.php?file=about_us [NC,L,QSA]
As you can see, I have to copy the following 2 lines for every RewriteRule:
RewriteCond %{HTTP_HOST} ^([a-z-]+)\.example\.com$ [NC]
RewriteCond %1 !^(javascript|css|images)$ [NC]
This works, but I want to know if there is a better solution?
What I want?
For example, when a user visits http://{subdomain-here}.example.com/about-us, the page index.php?file=about_us must show up. For every subdomain, except for the subdomains javascript, css and images.
Edit 1: If a visitors goes to http://javascript.example.com/about-us, the browser should give a 404 error.
Edit 2: a "general" regex (e.g. (.*)) will not work because the name of the file in the URL is not always the same as the original filename. http://subdomain.example.com/about-us should point to index.php?file=about_us (see the _) and not to index.php?file=about-us.

Answer 1

You can apply the opposite logic
RewriteEngine on
# Don't touch anything when it comes to those 3 subdomains
RewriteCond %{HTTP_HOST} ^(?:javascript|css|images)\.example\.com$ [NC]
RewriteRule ^ - [L]
# If we reach this part, this means we're not in the 3 subdomains restriction
RewriteRule ^$ /index.php?file=index [NC,L]
RewriteRule ^language$ /index.php?file=language [NC,L]
RewriteRule ^about-us$ /index.php?file=about_us [NC,L]
You can see that as an equivalent to
if subdomain in (javascript, css, images)
return
do something here for other subdomains

Answer 2

You can use this
RewriteEngine on
RewriteCond %{HTTP_HOST} ^([a-z-]+)\.example\.com$ [NC]
RewriteCond %1 !^(javascript|css|images)$ [NC]
RewriteRule ^(.*) index.php?file=$1 [NC,L,QSA]
or the following
:
RewriteEngine on
RewriteCond %{HTTP_HOST} !^(javascript|css|images) [NC]
RewriteRule ^(.*) index.php?file=$1 [NC,L,QSA]