Find unused css

unused_css.rb

css = File.read 'app/assets/stylesheets/new_web/app.css'
classes = css.scan /(?<=\.)[a-z][\w_-]+/

code = Dir.glob('app/views/static_pages/*').unshift 'app/views/layouts/new_web.html.erb'
code = code + Dir.glob('app/assets/javascripts/new_web/*')

markups = code.map { File.read _1 }

unused = classes.select do |css_class|
  markups.none? { _1.include? css_class }
end.uniq

unused.each { p _1 }