Phonegap

function onLoad(){
        document.addEventListener('deviceready', function() {
            document.addEventListener("backbutton", ShowExitDialog, false);
        }, false);
    }

function ShowExitDialog() {
    navigator.notification.confirm(
        ("Are you sure you want to exit ?"),
        alertexit,
        'Exit',
        'Ya,Tidak'
    );
}

function alertexit(button){
    if(button=="1" || button==1){
        device.exitApp();
    }
}