Introduce serviceWorker, disabled by default

1 files changed, 44 insertions, 0 deletions

diff --git a/static/sw.js b/static/sw.js
new file mode 100644
index 0000000..d42b04c
--- /dev/null
+++ b/static/sw.js
@@ -0,0 +1,44 @@
+self.addEventListener("install", function (event) {
+  self.skipWaiting();
+});
+
+self.addEventListener("fetch", (event) => {
+  const cacheName = self.location.pathname
+  const request = event.request;
+
+  if (request.method !== "GET") {
+    return;
+  }
+
+  /**
+   * @param {Response} response
+   * @returns {Promise<Response>}
+   */
+  function saveToCache(response) {
+    if (cacheable(response)) {
+      return caches
+        .open(cacheName)
+        .then((cache) => cache.put(request, response.clone()))
+        .then(() => response);
+    } else {
+      return response;
+    }
+  }
+
+  /**
+   * @param {Error} error
+   */
+  function serveFromCache(error) {
+    return caches.open(cacheName).then((cache) => cache.match(request.url));
+  }
+
+  /**
+   * @param {Response} response
+   * @returns {Boolean}
+   */
+  function cacheable(response) {
+    return response.type === "basic" && response.ok && !response.headers.has("Content-Disposition")
+  }
+
+  event.respondWith(fetch(request).then(saveToCache).catch(serveFromCache));
+});