peter-tanner.github.io/_javascript/pwa/sw.js

import { baseurl } from '../../_config.yml';

importScripts(`${baseurl}/assets/js/data/swconf.js`);

const purge = swconf.purge;

function verifyUrl(url) {
  const requestPath = new URL(url).pathname;

  for (const path of swconf.denyPaths) {
    if (requestPath.startsWith(path)) {
      return false;
    }
  }
  return true;
}

self.addEventListener('install', (event) => {
  if (purge) {
    return;
  }

  event.waitUntil(
    caches.open(swconf.cacheName).then((cache) => {
      return cache.addAll(swconf.resources);
    })
  );
});

self.addEventListener('activate', (event) => {
  event.waitUntil(
    caches.keys().then((keyList) => {
      return Promise.all(
        keyList.map((key) => {
          if (purge) {
            return caches.delete(key);
          } else {
            if (key !== swconf.cacheName) {
              return caches.delete(key);
            }
          }
        })
      );
    })
  );
});

self.addEventListener('message', (event) => {
  if (event.data === 'SKIP_WAITING') {
    self.skipWaiting();
  }
});

self.addEventListener('fetch', (event) => {
  if (event.request.headers.has('range')) {
    return;
  }

  event.respondWith(
    caches.match(event.request).then((response) => {
      if (response) {
        return response;
      }

      return fetch(event.request).then((response) => {
        const url = event.request.url;

        if (purge || event.request.method !== 'GET' || !verifyUrl(url)) {
          return response;
        }

        // See: <https://developers.google.com/web/fundamentals/primers/service-workers#cache_and_return_requests>
        let responseToCache = response.clone();

        caches.open(swconf.cacheName).then((cache) => {
          cache.put(event.request, responseToCache);
        });
        return response;
      });
    })
  );
});