New feature: PWA

sw.js

@@ -0,0 +1,49 @@
+---
+layout: compress
+# Chirpy v2.2
+# https://github.com/cotes2020/jekyll-theme-chirpy
+# © 2020 Cotes Chung
+# MIT Licensed
+---
+
+self.importScripts('{{ "/assets/data/cache-list.js" | relative_url }}');
+
+var cacheName = 'chirpy-{{ "now" | date: "%Y%m%d.%H%M" }}';
+
+self.addEventListener('install', (e) => {
+  self.skipWaiting();
+  e.waitUntil(
+    caches.open(cacheName).then((cache) => {
+      return cache.addAll(cacheList);
+    })
+  );
+});
+
+
+self.addEventListener('fetch', (e) => {
+  e.respondWith(
+    caches.match(e.request).then((r) => {
+      /* console.log('[Service Worker] Fetching resource: ' + e.request.url); */
+      return r || fetch(e.request).then((response) => {
+        return caches.open(cacheName).then((cache) => {
+          /* console.log('[Service Worker] Caching new resource: ' + e.request.url); */
+          cache.put(e.request, response.clone());
+          return response;
+        });
+      });
+    })
+  );
+});
+
+
+self.addEventListener('activate', (e) => {
+  e.waitUntil(
+    caches.keys().then((keyList) => {
+          return Promise.all(keyList.map((key) => {
+        if(key !== cacheName) {
+          return caches.delete(key);
+        }
+      }));
+    })
+  );
+});