Extend Laravel for {{}} in js,css and php files

The short answer is no because the blade files aren't served directly as static assets the way JS and CSS files are, they're compiled into more basic php templates, which are still not served directly because dynamic data has to be injected into them... but js and css files are served directly by the webserver, not parsed by php.

I think it would be and already is possible for js. See https://github.com/aaronlord/laroute. I think it would be even be possible on the fly. https://github.com/GrahamCampbell/Laravel-HTMLMin minifies on the fly and another fork could be replacing the placeholders

I think the real question to be asked here is why? What are you hoping to achieve by using blade syntax in js and css files.. most likely there's a better solution.