Emit 'storage-update' events on local storage update

assets/js/utils/store.ts

@@ -4,10 +4,18 @@
 
 export const lastUpdatedSuffix = '__lastUpdated';
 
+// We use this detached <div> element purely as an event bus to dispatch storage update
+// events. It is needed because the default 'stroge' event dispatched on the window
+// isn't triggered when the same page updates the storage.
+const localUpdates = document.createElement('div');
+
+type StorageUpdateEvent = CustomEvent<string>;
+
 export default {
   set(key: string, value: unknown) {
     try {
       localStorage.setItem(key, JSON.stringify(value));
+      this.dispatchStorageUpdateEvent(key);
       return true;
     } catch {
       return false;
@@ -27,12 +35,18 @@ export default {
   remove(key: string) {
     try {
       localStorage.removeItem(key);
+      this.dispatchStorageUpdateEvent(key);
       return true;
     } catch {
       return false;
     }
   },
 
+  dispatchStorageUpdateEvent(key: string) {
+    const event: StorageUpdateEvent = new CustomEvent('storage-update', { detail: key });
+    localUpdates.dispatchEvent(event);
+  },
+
   // Watch changes to a specified key - returns value on change
   watch<Value = unknown>(key: string, callback: (value: Value | null) => void) {
     const handler = (event: StorageEvent) => {
@@ -42,6 +56,12 @@ export default {
     return () => window.removeEventListener('storage', handler);
   },
 
+  // `null` key means the store was purged with `localStorage.clear()`
+  watchAll(callback: (key: null | string) => void) {
+    window.addEventListener('storage', event => callback(event.key));
+    localUpdates.addEventListener('storage-update', event => callback((event as StorageUpdateEvent).detail));
+  },
+
   // set() with an additional key containing the current time + expiration time
   setWithExpireTime(key: string, value: unknown, maxAge: number) {
     const lastUpdatedKey = key + lastUpdatedSuffix;