Sync StorageProxyObjects between windows

src/lib.ts

@@ -4,6 +4,12 @@ import onChange from 'on-change';
 
 // --- Types & constants ---------------------------------------------------- //
 
+/** Web storage targets: `localStorage` and `sessionStorage`. */
+export enum StorageTarget {
+  Local = 'localStorage',
+  Session = 'sessionStorage',
+}
+
 const namespaceSymbol = Symbol('namespaceSymbol');
 const isStorageProxy = Symbol('isStorageProxy');
 const storageTargetSymbol = Symbol('storageTargetSymbol');
@@ -12,12 +18,6 @@ const storageProxyIntegrityKey = '__storageProxyIntegrity';
 
 const isStorageAvailableCache: Map<StorageTarget, boolean> = new Map();
 
-/** Web storage targets: `localStorage` and `sessionStorage`. */
-export enum StorageTarget {
-  Local = 'localStorage',
-  Session = 'sessionStorage',
-}
-
 /** The object type created by `StorageProxy.createLocalStorage()` and `StorageProxy.createSessionStorage()`. */
 export type StorageProxyObject<TStorageDefinitions> = Partial<TStorageDefinitions> & {
   readonly [namespaceSymbol]: string;
@@ -119,6 +119,17 @@ function createProxy<TStorageDefinitions extends any>(
     },
   });
 
+  // Sync a `StorageProxyObject` if changes occur to its namespace in another
+  // window.
+  window.addEventListener('storage', ev => {
+    if (StorageProxy.isStorageAvailable(storageTarget)) {
+      if (ev.key === namespace && ev.storageArea === window[storageTarget]) {
+        const data = getDataFromStorage(namespace, storageTarget);
+        for (const [key, value] of Object.entries(data)) storageProxy[key] = value;
+      }
+    }
+  });
+
   if (defaults) {
     for (const [key, value] of Object.entries(defaults)) {
       if (isUndefined(data[key])) {

test/src/storage-proxy.spec.ts

@@ -200,6 +200,7 @@ export class StorageProxyTestFixture {
 
   @Test('Clearing `StorageProxy` removes all keys from both `WebStorage` and the local object')
   public clearStorageTest() {
+    localStorage.clear();
     StorageProxy.clearStorage(this.lStore);
 
     Expect(this.lStore.alreadySetDefault).toBeNull();