Fallback to default image

[chenxsan]

I'm not sure how to define fallback image for some url patterns as https://jakearchibald.com/2014/offline-cookbook/#generic-fallback describe in sw-precache.

I had default_profile_image.png cached in staticFileGlobs. When offline, if profile images are not in cache, then fallback to default_profile_image.png.

It seems runtimeCaching is the right place to configure my fallback image then I have to write my own request handler, it would be really complex.

Wondering if there's any better way to do it in sw-precache.

[chenxsan]

I think it can be done with sw-toolbox directly as https://developers.google.com/web/showcase/2015/service-workers-iowa#speaker_profile_images showed.

[chenxsan]

Just pass the function to handler like:

    runtimeCaching: [
      {
        urlPattern: /profile_images.*normal\./,
        handler: function (request, values, options) {
          return toolbox.networkOnly(request).catch(function () {
            return toolbox.cacheOnly(new Request('/img/default_profile_2_normal.png'))
          })
        }
      },