We could extract the current ` before_filter -> { @css_framework = :bootstrap }, :only => [...]` to something like (in ApplicationController):

```ruby
def self.use_bootstrap_for *routes
   before_filter -> {
     @css_framework = :bootstrap
     gon.bootstrap = true
   }, only: routes.flatten
end
```

Which could be used as `use_bootstrap_for :index, :show` and should allow a check in Javascript like `if (gon.bootstrap == true)`