initial commit

static/fetch.mjs

@@ -0,0 +1,37 @@
+import localforage from 'https://cdn.jsdelivr.net/npm/localforage/+esm'
+/** @type {Storage} */
+const cache=localforage.createInstance({name:import.meta.url})
+// make sure we don't lose the bultin fetch
+const fetch=window.fetch
+
+/**
+ * `fetch` with an infinite cache
+ * @param {RequestInfo} resource 
+ * @param {RequestInit} options 
+ * @returns {Promise<Response>}
+ */
+export default async function fetchCached(resource,options={}){
+    if('body' in options){
+        cache.setItem(resource.toString(),options.body)
+        return fetch(resource,options)
+    }
+    if('method' in options && options.method==='DELETE'){
+        cache.removeItem(resource.toString())
+    }
+    return fetch(resource,options).then(async response=>{
+        if(!response.ok){
+            throw response
+        }
+        cache.setItem(resource,await response.clone().blob())
+        return response
+    }).catch(async error=>{
+        const body=await cache.getItem(resource.toString())
+        if(body){
+            return new Response(body)
+        }
+        if(error instanceof Response){
+            return error
+        }
+        throw error
+    })
+}