registerServiceWorker.js

if ('serviceWorker' in navigator) {
  window.addEventListener('load', function() {
    navigator.serviceWorker.register('/sw.js')
    .then(function(registration) {
      // Registration was successful
      console.log('ServiceWorker registration successful ');
      }).catch(function(err) {
      // registration failed :(
      console.log('ServiceWorker registration failed: ', err);
  });
});