```ruby
require 'rubygems'
require 'sinatra'
require 'json'
require 'fileutils'

# copy rails.js file from src to vendor directory
source_file = File.join( File.dirname(__FILE__) ,  '..', 'src', 'rails.js')
dest_file = File.join(File.dirname(__FILE__), 'public', 'vendor', 'rails.js')
FileUtils.cp(source_file, dest_file)

after do
  ctype = request.xhr? ? 'application/json' : 'text/html'
  content_type ctype, :charset => 'utf-8'
end

get '/' do
  erb :index
end

get '/show' do
  if request.xhr?
    {:hello => :sexy, :request_env => request.env}.to_json
  else
    '/show requested without ajax'
  end
end

get '/error' do
  status 403
end

post '/update' do
  if request.xhr?
    {:hello => :sexy, :request_env => request.env}.to_json
  else
    '/update requested without ajax'
  end
end

get '/iframe' do
  erb :iframe
end

get '/iframe-csrf' do
  erb :iframe_csrf
end

delete '/delete' do
  "/delete was invoked with delete verb. params is #{params.inspect}"
end
```

Copy src/rails.js into where it will be served up to the browser every time the index page is refreshed.
user
```ruby
require 'rubygems'
require 'sinatra'
require 'json'
require 'fileutils'

# copy rails.js file from src to vendor directory
source_file = File.join( File.dirname(__FILE__) ,  '..', 'src', 'rails.js')
dest_file = File.join(File.dirname(__FILE__), 'public', 'vendor', 'rails.js')
FileUtils.cp(source_file, dest_file)

after do
  ctype = request.xhr? ? 'application/json' : 'text/html'
  content_type ctype, :charset => 'utf-8'
end

get '/' do
  FileUtils.cp(source_file, dest_file)
  erb :index
end

get '/show' do
  if request.xhr?
    {:hello => :sexy, :request_env => request.env}.to_json
  else
    '/show requested without ajax'
  end
end

get '/error' do
  status 403
end

post '/update' do
  if request.xhr?
    {:hello => :sexy, :request_env => request.env}.to_json
  else
    '/update requested without ajax'
  end
end

get '/iframe' do
  erb :iframe
end

get '/iframe-csrf' do
  erb :iframe_csrf
end

delete '/delete' do
  "/delete was invoked with delete verb. params is #{params.inspect}"
end
```
assistant