service-worker.js

const CACHE_NAME = 'kana-go-v1';
const ASSETS = [
  '/',
  '/index.html',
  '/style.css',
  '/script.js',
  '/jpChars.js',
  '/icon-192.png',
  '/icon-512.png'
];

self.addEventListener('install', (e) => {
  e.waitUntil(
    caches.open(CACHE_NAME).then((cache) => cache.addAll(ASSETS))
  );
});

self.addEventListener('fetch', (e) => {
  e.respondWith(
    caches.match(e.request).then((response) => response || fetch(e.request))
  );
});

self.addEventListener('activate', (e) => {
  e.waitUntil(
    caches.keys().then((keyList) => {
      return Promise.all(
        keyList.map((key) => {
          if (key !== CACHE_NAME) {
            return caches.delete(key);
          }
        })
      );
    })
  );
});