JS: visibilityChange
more at: http://stackoverflow.com/a/15846434/1250044
by Juan Muñoz
JavaScript
window.addEventListener('visibilitychange',()=> {
switch( document.visibilityState){
case 'prerender':
document.body.innerHTML = ("tabs is pre-rendering")
break;
case 'hidden':
document.body.innerHTML = ("tabs is hidden")
break;
case 'visible':
document.body.innerHTML = ("tabs is visible")
break;
}
})