workbox-window method to trigger SW update check

Library Affected: workbox-sw, workbox-window

Browser & Platform: all browsers

Issue or Feature Request Description: If I try to instantiate workbox a second time no events are fired. What I basically want to achieve is that the user presses a button, the service worker should reload and thus he will check for updates. It seems that currently the service worker can only be instantiated once. Appending a random timestamp in the file name causes the service worker to always download everything again.

There should be a method that just checks for updates of the service worker itself.

  const workbox = new Workbox(`/service-worker.js`, {
    scope: '/',
  })
  await workbox.register()

[daffinm]

It would be really useful, from a UX point of view, if this new update() method could return, somehow, a flag indicating if an update was found or not. If this update check is initiated by the user, for instance by clicking a ‘Check for Updates’ button, this would allow them to be informed that ‘No updates were found’. Otherwise nothing seems to happen…

[jaulz]

I gave a first try and created a PR which introduces the new update method.

By any chance can you tell me how you usually create examples to reproduce cases like these?