Using fetch from ClojureScript

fetch.cljs

(ns js-fetch
  (:require [promesa.core :as p]
            [clojure.string :as str])

(defn serialize
  [content-type data]
  (pr-str data))

(defn deserialize
  [content-type text]
  (cljs.reader/read-string text))

(defn fetch
  "Returns promise a map with keys :headers and :body."
  [{:as args :keys [method uri params headers]}]
  (let [{:keys [content-type]} headers
        state (atom {})
        method (str/lower-case (name method))
        opts (cond-> {:method method
                      :headers headers
                      :mode "cors"}
               (and (not (#{"get" "head"} method))
                    params)
               (assoc :body (serialize content-type params))
               true clj->js)]
    ;; (log/infof "fetch args: %s" args)
    ;; (log/infof "fetch opts: %s" opts)
    ;; (.log js/console opts)
    (-> (js/fetch uri opts)
        (p/then (fn [response]
                  (let [headers (aget response "headers")]
                    (swap! state assoc :headers
                           (reduce (fn [m k]
                                     (assoc m k (.get headers k)))
                                   {}
                                   (es6-iterator-seq (.keys headers)))))
                  (.text response)))
        (p/then (fn [text]
                  (let [{:keys [content-type]} (:headers @state)
                        body                   (deserialize content-type text)]
                    {:headers headers
                     :body    body}))))))