cors.clj

(ns api-project.cors)

(def cors-headers
  "Generic CORS headers"
  {"Access-Control-Allow-Origin"  "*"
   "Access-Control-Allow-Headers" "*"
   "Access-Control-Allow-Methods" "GET"})

(defn preflight?
  "Returns true if the request is a preflight request"
  [request]
  (= (request :request-method) :options))

(defn all-cors
  "Allow requests from all origins - also check preflight"
  [handler]
  (fn [request]
    (if (preflight? request)
      {:status 200
       :headers cors-headers
       :body "preflight complete"}
      (let [response (handler request)]
        (update-in response [:headers]
                   merge cors-headers )))))

🍨

FYI, since I just got burned by this: wildcard "*" for "Access-Control-Allow-Headers" might not be supported by all browsers see here http://stackoverflow.com/questions/13146892/cors-access-control-allow-headers-wildcard-being-ignored

love it

Searched for a while and this worked for me also. Thank you!

Thank you so much for this gist. I've had a maddening time getting ring-cors to do ... anything at all based on the documented example, and this got my CORS settings for an http-kit/compojure server working finally!

Like @andyfry01 it was maddening for me to get ring-cors working. Thank you for this Gist!