polyfill-service/polyfills/document.visibilityState/polyfill.js

A polyfill combinator

// PageVisibility
(function () {
	var prefix = document.webkitVisibilityState ? 'webkit' : document.mozVisibilityState ? 'moz' : null;

	function normalizeState () {
		document.hidden = document[prefix + 'Hidden'];
		document.visibilityState = document[prefix + 'VisibilityState'];
	}

	if (!prefix) {
		return;
	}

	normalizeState();

	document.addEventListener(prefix + 'visibilitychange', function () {
		normalizeState();
		document.dispatchEvent(new CustomEvent('visibilitychange'));
	});

}());