index.js

if ('serviceWorker' in navigator) {
  navigator.serviceWorker.register('/service-workerw.js').then(function(registration) {
    // register success
    console.log('ServiceWorker registration successful with scope: ', registration.scope);
  }).catch(function(err) {
    // registration failed :(
    console.log('ServiceWorker registration failed: ', err);
  });
}