getHiddenProp（） 浏览器状态切换改变

<script>
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 getVisibilityState() {
var prefixes = ['webkit', 'moz', 'ms', 'o'];
if ('visibilityState' in document) return 'visibilityState';
for (var i = 0; i < prefixes.length; i++) {
if ((prefixes[i] + 'VisibilityState') in document)
return prefixes[i] + 'VisibilityState';
}
// otherwise it's not supported
return null;
}

function isHidden() {
var prop = getHiddenProp();
if (!prop) return false;

return document[prop];
}

// use the property name to generate the prefixed event name
var visProp = getHiddenProp();
if (visProp) {
var evtname = visProp.replace(/[H|h]idden/, '') + 'visibilitychange';
document.addEventListener(evtname, function () {
document.title = document[getVisibilityState()]+"状态";
},false);
}

// Set the initial value
document.title = document[getVisibilityState()]+"状态";
</script>