How can I translate the javascript code to clojurescript?

Question

I would like to use capacitor/app to get the state (background or active) of my app on iOS. My project is based on Clojurescript so it is necessary to translate the following javascript code to clojurescript one.

• Javascript

import { App } from '@capacitor/app';

App.addListener('appStateChange', ({ isActive }) => {
  console.log('App state changed. Is active?', isActive);
});

• translated clojurescript

(ns js.sample
  (:require ["@capacitor/app" :refer [App]]))

(.addListener App "appStateChange"
                  #((fn [isActive]
                      (js/console.log isActive))))

I suppose I would get isActive as true or false, but I constantly get an undefined output. What is wrong with my code? Appreciate for any help.

Answer 1

(.addListener App "appStateChange"
                  (fn [^js event]
                    (js/console.log (.-isActive event))))

As cfrick's comment mentions, #(...) is not needed there. #(...) is basically just a shorthand for (fn [...] ...), and you already have a function there.

In JS, {isActive} in a function's signature means that isActive will be assigned to the value of the isActive field of the object that was passed to the function.

^js in CLJS marks the name that follows it as one containing a JS object. It's necessary to make sure that things like isActive don't end up being renamed by the compiler during production build optimizations. It shouldn't be necessary in this case because isActive name is not something that you or some library invented but rather a name coming from JS API. But I still find it to be a good practice to delineate such things. (^js shouldn't be used with goog imports, however.)