p {
width: 100px;
height: 50px;
padding: 20px;
border: 1px solid;
<!doctype html>
<html lang="en">
<title>Mary's Maple Bar Fast-Baking Recipe</title>

// Feature detection
if ('serviceWorker' in navigator) {
// Register a service worker
// A service worker JS file is separate
// PaymentManager requires the service worker to be active.
// One simple method to activate a service worker is through
// a `ready` promise.
const registration = await navigator.serviceWorker.ready;