<script src="<module-dir>/lib/WebModule.js"></script>
<script src="<module-dir>/lib/PageVisibilityEvent.js"></script>
<script>
if (PageVisibilityEvent.enable) {
    PageVisibilityEvent.on(function(hidden) {
        console.log(hidden ? "page hide"
                           : "page show");
    });
}
</script>