service-worker-installer.js

if ('serviceWorker' in navigator) {
  navigator.serviceWorker
    .register('/service-worker.js', {
      scope: '/'
    })
    .then(function (reg) {
      if (reg.installing) {
        console.log('Service worker installing');
      } else if (reg.waiting) {
        console.log('Service worker installed');
      } else if (reg.active) {
        console.log('Service worker active');
      }
    }).catch(function (error) {
      // registration failed
      console.log(`Registration failed with ${error}`);
    });
}