document.addEventListener('visibilitychange', function() {

console.log(isHidden() + "-" + new Date().toLocaleTimeString())

});

function getHiddenProp() {

var prefixes = ['webkit', 'moz', 'ms', 'o'];

// if 'hidden' is natively supported just return it

if('hidden' in document) return 'hidden';

// otherwise loop over all the known prefixes until we find one

for(var i = 0; i < prefixes.length; i++) {

if((prefixes[i] + 'Hidden') in document)

return prefixes[i] + 'Hidden';

}

// otherwise it's not supported

return null;

}

function isHidden() {

var prop = getHiddenProp();

if(!prop) return false;

return document[prop];

}