gistfile1.rb

module Rack
  class AddAccessControlHeader
    def initialize app, opts
      @app = app
      @extensions = opts
    end

    def call(env)
      response = @app.call(env)
      headers = Utils::HeaderHash.new(response[1])

      ext = env["PATH_INFO"].split(".")[-1]
      headers["Access-Control-Allow-Origin"] = '*' if @extensions.include?(ext)

      response[1] = headers
      response
    end
  end 
end