<!DOCTYPE HTML> <html> <head> <meta http-equiv="Content-type" content="text/html;charset=UTF-8"> <script> function waitOnWorkerMessage(type) { return new Promise(function(res, rej) { function onMessage(e) { if (e.data.type == type) { navigator.serviceWorker.removeEventListener("message", onMessage); (e.data.okay == "yes" ? res : rej)(e.data); } } navigator.serviceWorker.addEventListener("message", onMessage); }); } </script> </head> <body> </body> </html>