fallback.js

'use strict'

self.fallback = async (request) => {
    // https://developer.mozilla.org/en-US/docs/Web/API/RequestDestination
    switch (request.destination) {
      case 'document':
        if (process.env.__PWA_FALLBACK_DOCUMENT__) return caches.match(process.env.__PWA_FALLBACK_DOCUMENT__, {ignoreSearch: true})
      case 'image':
        if (process.env.__PWA_FALLBACK_IMAGE__) return caches.match(process.env.__PWA_FALLBACK_IMAGE__, {ignoreSearch: true})
      case 'audio':
        if (process.env.__PWA_FALLBACK_AUDIO__) return caches.match(process.env.__PWA_FALLBACK_AUDIO__, {ignoreSearch: true})
      case 'video':
        if (process.env.__PWA_FALLBACK_VIDEO__) return caches.match(process.env.__PWA_FALLBACK_VIDEO__, {ignoreSearch: true})
      case 'font':
        if (process.env.__PWA_FALLBACK_FONT__) return caches.match(process.env.__PWA_FALLBACK_FONT__, {ignoreSearch: true})
      case '':
        if (process.env.__PWA_FALLBACK_DATA__ && request.url.match(/\/_next\/data\/.+\/.+\.json$/i)) return caches.match(process.env.__PWA_FALLBACK_DATA__, {ignoreSearch: true})
      default:
        return Response.error()
    };
  }