Javascript redirect when device has restarted

Contents

    Over the past few months I have been building a sensor device with a embedded webserver for configuration and reporting. When a user saves a configuration to the device the device needs to be restarted before the changes come in to effect.

    While the device is restarting the webserver is unreachable and the users get a blank page or 404 pages, this is bad for the users. So I created this simple script to check to see if the device has been restarted correctly then redirect the users to the correct page. This script uses JQuery

    Script: Redirect on reboot

    <script type="text/javascript">
    		function UrlExists(url) {
    			var http = new XMLHttpRequest();
    			http.open('HEAD', url, false);
    			http.send();
    			return http.status!=404;
    		}
    
    		var checkCount = 0 ; 
    
    		function CheckServerUp(){
    			checkCount++; 
    			$('#status').text('Checking. ' + checkCount ) ;			
    			if( checkCount > 30 ) {
    				$('#Error').html('The device is taking a long time to reboot, <a href="/refresh2.htm">Click here to continue</a>' + checkCount ) ;
    			}
    
    			if( UrlExists( "refresh2.htm" ) ) {
    				$('#status').text('Device running, redirecting...') ; 
    				window.location.replace( "/refresh2.htm" );				
    			}
    		};
    
    		$(document).ready(function(){
    			setInterval( "CheckServerUp()", 1000 );			
    		});
    	</script>