- views
 - index.pug
- sw.js
- public
 - js
  - main.js
- index.js

if ('serviceWorker' in navigator) {
    window.addEventListener('load', function() {
        navigator.serviceWorker.register('./sw.js').then(function(registration) {
            // Registration was successful
            console.log('Service Worker registration successful with scope: ', registration.scope);

            // console.log('Service Worker registration successful with scope: ', registration.scope);
        }, function(err) {
            // registration failed :(
            console.log('ServiceWorker registration failed: ', err);
        });
    });
}

ServiceWorker registration failed:  TypeError: Failed to register a ServiceWorker: A bad HTTP response code (404) was received when fetching the script.