if (typeof window.document.hidden !== 'undefined') {
hidden = 'hidden';
}
else if (typeof window.document.msHidden !== 'undefined') {
hidden = 'msHidden';
}
else if (typeof window.document.webkitHidden !== 'undefined') {
hidden = 'webkitHidden';
}
doVisualUpdates = !window.document[hidden];
reference: https://developer.mozilla.org/en-US/docs/Web/API/Page_Visibi...