Configure Sinatra for CORS (Whitelist from any domain, don't actually do this in production)

sinatra_with_cors.rb

require 'sinatra'

set :server, 'webrick'

before do
  response.headers['Access-Control-Allow-Origin'] = '*'
end

options '*' do
  response.headers['Access-Control-Allow-Methods'] = 'GET, POST, PUT, PATCH, DELETE, OPTIONS'
  response.headers['Access-Control-Allow-Headers'] = 'content-type,x-csrf-token,x-requested-with'

  200
end