document.addEventListener("visibilitychange", () => { if (document.hidden) { // tab is changed } else { // tab is active } });let browser_active = ((typeof document.hasFocus != 'undefined' ? document.hasFocus() : 1) ? 1 : 0); if (!browser_active) { // active } var interval_id; $(window).focus(function() { if (!interval_id) interval_id = setInterval(hard_work, 1000); }); $(window).blur(function() { clearInterval(interval_id); interval_id = 0; });