How do I work device button 'back' in game?

var init = function () {
    // TODO:: Do your initialization job
    console.log("init() called");

    // add eventListener for tizenhwkey
    document.addEventListener('tizenhwkey', function(e) {
        if(e.keyName == "back")
            tizen.application.getCurrentApplication().exit();
    });
};[/code:27lcux2t]

[img="http://c2community.ru/imagehosting/images/2014/Jul/04/1.jpg"]

However,C2  ignores it somehow (main.js) , namely probably as follows:
  file index:

[code:27lcux2t]// Pause and resume on page becoming visible/invisible
		function onVisibilityChanged() {
			if (document.hidden || document.mozHidden || document.webkitHidden || document.msHidden)
				cr_setSuspended(true);
			else
				cr_setSuspended(false);
		};
		
		document.addEventListener("visibilitychange", onVisibilityChanged, false);
		document.addEventListener("mozvisibilitychange", onVisibilityChanged, false);
		document.addEventListener("webkitvisibilitychange", onVisibilityChanged, false);
		document.addEventListener("msvisibilitychange", onVisibilityChanged, false);
		
    </script>[/code:27lcux2t]
[img="http://c2community.ru/imagehosting/images/2014/Jul/04/2.jpg"]
Question - How to make exit of the game on the first page of the game by clicking the back button device, and in other cases would go to the previous page game (Layout)?