Hide content of android app created with cordova when user presses the menu button

I have an android app that I'm building with cordova and I want to hide the content of the app when user presses the menu button or when the app loses focus. The code I use is in JavaScript and it works in chrome browser but it does not work when I run the android app in a physical device. Please send me a working example. Just a simple apk that hides the content when the menu button is pressed. Thank you.