register.js

import Eventbus from '../launcher/services/eventbus'

// This comes from https://developers.google.com/web/tools/workbox/guides/advanced-recipes
// It allows activating the new service worker right away on reload
if ('serviceWorker' in navigator) {
  window.addEventListener('load', function () {
    navigator.serviceWorker.register('/sbvr-service-worker.js')
    .then(function (registration) {
        // Track updates to the Service Worker.
      if (!navigator.serviceWorker.controller) {
        // The window client isn't currently controlled so it's a new service
        // worker that will activate immediately
        return
      }
      // When the user asks to refresh the UI, we'll need to reload the window
      var preventDevToolsReloadLoop
      navigator.serviceWorker.addEventListener('controllerchange', function (event) {
        // Ensure refresh is only called once.
        // This works around a bug in "force update on reload".
        if (preventDevToolsReloadLoop) return
        preventDevToolsReloadLoop = true
        window.location.reload()
      })
      Eventbus.$on('sw:check-update', () => {
        registration.update && registration.update()
      })

      onNewServiceWorker(registration, function () {
        showRefreshUI(registration)
      })
    })
  })
}

function showRefreshUI (registration) {
  // var button = document.createElement('button')
  // button.style.position = 'absolute'
  // button.style.bottom = '24px'
  // button.style.left = '24px'
  // button.textContent = 'This site has updated. Please click here to see changes.'
  //
  // button.addEventListener('click', function () {
  //   if (!registration.waiting) {
  //     // Just to ensure registration.waiting is available before
  //     // calling postMessage()
  //     return
  //   }
  //
  //   button.disabled = true
  registration.waiting.postMessage('skipWaiting')
  // })

  // document.body.appendChild(button)
};

function onNewServiceWorker (registration, callback) {
  if (registration.waiting) {
    // SW is waiting to activate. Can occur if multiple clients open and
    // one of the clients is refreshed.
    return callback()
  }

  function listenInstalledStateChange () {
    registration.installing.addEventListener('statechange', function (event) {
      if (event.target.state === 'installed') {
        // A new service worker is available, inform the user
        callback()
      }
    })
  };

  if (registration.installing) {
    return listenInstalledStateChange()
  }

  // We are currently controlled so a new SW may be found...
  // Add a listener in case a new SW is found,
  registration.addEventListener('updatefound', listenInstalledStateChange)
}

How could I use your logic without using (import Eventbus from '../launcher/services/eventbus')?

Use native functions.