Cross Origin Requests (CORS)

If your API and client live on different domains, you will need to configure your Rails API to allow cross origin requests. The rack-cors gem can be used to accomplish this.
The following dangerous example will allow cross domain requests from any domain. Make sure to whitelist only the needed domains.

Example rack-cors configuration:

# gemfile
gem 'rack-cors', :require => 'rack/cors'
# config/application.rb
module YourApp
class Application < Rails::Application
config.middleware.use Rack::Cors do
allow do
origins '*'
resource '*',
headers: :any,
expose: ['access-token', 'expiry', 'token-type', 'uid', 'client'],
methods: [:get, :post, :options, :delete, :put]
Make extra sure that the Access-Control-Expose-Headers includes access-token, expiry, token-type, uid, and client (as is set in the example above by the:expose param). If your client experiences erroneous 401 responses, this is likely the cause.
CORS may not be possible with older browsers (IE8, IE9). I usually set up a proxy for those browsers. See the ng-token-auth readme or the jToker readme for more information.