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;
});