CLJS uses js promises

promise_test.cljs

(defn subtask+ []
  (js/Promise. (fn [resolve]
                   (js/setTimeout #(resolve :success) 5000)))
 )

(defn main []
  (-> (subtask+)
      (.then  (fn [result] (println "Got " result) ))
      (.catch (fn [e] (println "Shit happend! " e )) )
  ))

(println "Start")
(main)
(println "End")

(defn subtask1+ []
  (js/Promise. (fn [resolve]
                   (js/setTimeout #(resolve :success) 5000)
                   (println "Subtask1+ at once! " )))
 )

(defn subtask2+ [arg]
  (js/Promise. (fn [resolve]
                   (js/setTimeout #(resolve :success) 3000)
                   (println "Subtask2+ at once! " )))
 )

(defn subtask3+ [arg]
  (js/Promise. (fn [resolve]
                   (js/setTimeout #(resolve :success) 4000)
                   (println "Subtask3+ at once! " )))
 )

(defn main []
  (-> (subtask+)
      (.then  (fn [result] (println "Got " result) ))
      (.catch (fn [e] (println "Shit happend! " e )) )
  ))

(defn composite-task []
  (-> (subtask1+)
      (.then  (fn [result] (subtask2+ result) ))
      (.then  (fn [result] (subtask3+ result) ))
      (.catch (fn [e] (println "Shit happend! " e )) )
  ))


(println "Start")
(composite-task)
(println "End")