Hi,
I need to use BackgroundMode plugin http://ionicframework.com/docs/v2/native/background-mode/ to call a function when the application enters background mode. But I can not figure out how to use on(eventName) 
Please, can anyone give me a hint?
You should be able to use it like so
BackgroundMode.on('activate', this.backgroundMethod());
I also could not find how to use this method and this is the correct syntax which i was looking for, thanks! Unfortunately, I ran into another problem https://github.com/driftyco/ionic-native/issues/437 So I tried to use document.addEventListener. Pause event works fine, but document.addEventListener("resume", onResume, false); is not executed right after opening the app (from multitasking menu) but user have to click on the screen 
I figured out that I do not need any plugin and I can use
this.platform.resume.subscribe(e => { this.onResume(); });