prof3ssorSt3v3/page-visibility.html

## page-visibility.html
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Page Visibility API</title>
    <meta name="viewport" content="width=device-width">
</head>
<body>
    <h1>Page Visibility API</h1>
    <p>As long as this tab is the one tab in the browser with focus then nothing happens. When the user switches to another tab that triggers the visibilitychange event on the document object.</p>
    <script>
        //document.hidden
        //document.addEventListener('visibilitychange', myfunc)
        //... webkitHidden  msHidden
        //... webkitvisibilitychange  msvisibilitychange
        let hidden, vChange;
        if( typeof document.hidden !== 'undefined'){
            hidden = 'hidden';
            vChange = 'visibilitychange';
        }else if(typeof document.webkitHidden !== 'undefined'){
            hidden = 'webkitHidden';
            vChange = 'webkitvisibilitychange';
        }else if(typeof document.msHidden !== 'undefined'){
            hidden = 'msHidden';
            vChange = 'msvisibilitychange';
        }else{
            //no support
            hidden = null;
            vChange = null;
        }
        if( hidden !== null){
            document.addEventListener(vChange, function(ev){

                console.log('visibilitychange', document[hidden]);

                if(document[hidden]){
                    //page has lost focus
                    //stop the audio or video
                }else{
                    //page has regained focus
                    //start the audio or video
                }
            });
        }
    </script>
</body>
</html>
	<!DOCTYPE html>
	<html lang="en">
	<head>
	<meta charset="UTF-8">
	<title>Page Visibility API</title>
	<meta name="viewport" content="width=device-width">
	</head>
	<body>
	<h1>Page Visibility API</h1>
	<p>As long as this tab is the one tab in the browser with focus then nothing happens. When the user switches to another tab that triggers the visibilitychange event on the document object.</p>
	<script>
	//document.hidden
	//document.addEventListener('visibilitychange', myfunc)
	//... webkitHidden msHidden
	//... webkitvisibilitychange msvisibilitychange
	let hidden, vChange;
	if( typeof document.hidden !== 'undefined'){
	hidden = 'hidden';
	vChange = 'visibilitychange';
	}else if(typeof document.webkitHidden !== 'undefined'){
	hidden = 'webkitHidden';
	vChange = 'webkitvisibilitychange';
	}else if(typeof document.msHidden !== 'undefined'){
	hidden = 'msHidden';
	vChange = 'msvisibilitychange';
	}else{
	//no support
	hidden = null;
	vChange = null;
	}
	if( hidden !== null){
	document.addEventListener(vChange, function(ev){

	console.log('visibilitychange', document[hidden]);

	if(document[hidden]){
	//page has lost focus
	//stop the audio or video
	}else{
	//page has regained focus
	//start the audio or video
	}
	});
	}
	</script>
	</body>
	</html>