Example of using JSONP with Sinatra

jsonpatra.rb

# http://snippets.aktagon.com/snippets/445-How-to-create-a-JSONP-cross-domain-webservice-with-Sinatra-and-Ruby

require 'sinatra/base'
require 'json/pure'

module JSONPatra
  class App < Sinatra::Base
    get "/" do
      callback = params['callback']
      json = { :hello => "world!" }.to_json
      
      content_type(callback ? :js : :json)
      response = callback ? "#{callback}(#{json})" : json
      
      response
    end
  end
end

run JSONPatra::App.new