fix(js-core): no longer throw error when localStorage is not available

Closes #17

projects/js-core/src/lib/persistence.spec.ts

@@ -6,7 +6,7 @@ describe('Persistence', () => {
     localStorage.removeItem(key);
   });
   afterEach(() => {
-    localStorage.removeItem(key);
+    localStorage?.removeItem(key);
   });
 
   it('works for the example in the docs', () => {
@@ -21,6 +21,22 @@ describe('Persistence', () => {
     expect(persistence.get()).toEqual({ name: 'Robert' });
   });
 
+  // this can happen in android webviews, where it's up to the embedding app to call `.setDomStorageEnabled()`
+  it('gracefully handles when localStorage is null', () => {
+    spyOnProperty(window, 'localStorage').and.returnValue(null);
+    const persistence = new Persistence('my key');
+
+    expect(() => {
+      persistence.put('ignored');
+    }).not.toThrowError();
+
+    expect(persistence.get()).toBeUndefined();
+
+    expect(() => {
+      persistence.clear();
+    }).not.toThrowError();
+  });
+
   describe('.put() & .get()', () => {
     it('can work with primitives', () => {
       const value = 42;

projects/js-core/src/lib/persistence.ts

@@ -1,6 +1,8 @@
 /**
  * Get and put objects from/to local storage. They will be (de)serialized as JSON, so be sure that's OK for your objects.
  *
+ * If localStorage is not available, all methods essentially act as noops.
+ *
  * ```ts
  *  // if 'my key' has never been used before
  *  const persistence = new Persistence('my key');
@@ -23,21 +25,21 @@ export class Persistence<T> {
    * Serializes `obj` and saves it in local storage.
    */
   put(obj: T): void {
-    localStorage.setItem(this.key, JSON.stringify(obj));
+    localStorage?.setItem(this.key, JSON.stringify(obj));
   }
 
   /**
    * Retrieves a deserialized copy of the saved object, or `undefined` if it has not been set.
    */
   get(): T {
-    const savedStr = localStorage.getItem(this.key);
-    return savedStr === null ? undefined : JSON.parse(savedStr);
+    const savedStr = localStorage?.getItem(this.key);
+    return savedStr == null ? undefined : JSON.parse(savedStr);
   }
 
   /**
    * Deletes the saved item from local storage.
    */
   clear(): void {
-    localStorage.removeItem(this.key);
+    localStorage?.removeItem(this.key);
   }
 }