Efficient client-side storage module for Angular:
- simplicity: simple API like native
localStorage, - perfomance: internally stored via the asynchronous
indexedDBAPI, - Angular-like: wrapped in RxJS
Observables, - security: validate data with a JSON Schema,
- compatibility: works around some browsers issues and heavily tested via GitHub Actions,
- documentation: API fully explained, and a changelog!
For now, Angular does not provide a client-side storage module, and almost every app needs some client-side storage. There are 2 native JavaScript APIs available:
The localStorage API is simple to use but synchronous, so if you use it too often,
your app will soon begin to freeze.
The indexedDB API is asynchronous and efficient, but it's a mess to use:
you'll soon be caught by the callback hell, as it does not support Promises yet.
Mozilla has done a very great job with the localForage library:
a simple API based on native localStorage,
but internally stored via the asynchronous indexedDB for performance.
But it's built in ES5 old school way and then it's a mess to include into Angular.
This module is based on the same idea as localForage, but built in ES6+
and additionally wrapped into RxJS Observables
to be homogeneous with other Angular modules.
Install the package, according to your Angular version:
# For Angular LTS (Angular >= 12):
ng add @ngx-builders/pwa-local-storageDone!
You should stick to these commands. If for any reason ng add does not work,
be sure to follow the manual installation guide,
as there are additionnal steps to do in addition to the package installation for some versions.
If you have multiple applications in the same project, as usual, you need to choose the project:
ng add @ngx-builders/pwa-local-storage --project yourprojectnameimport { StorageMap } from '@ngx-builders/pwa-local-storage';
@Injectable()
export class YourService {
constructor(private storage: StorageMap) {}
}This service API follows the
new standard kv-storage API,
which is similar to the standard Map API, and close to the
standard localStorage API,
except it's based on RxJS Observables instead of Promises:
class StorageMap {
// Write
set(index: string, value: any): Observable<undefined> {}
delete(index: string): Observable<undefined> {}
clear(): Observable<undefined> {}
// Read (one-time)
get(index: string): Observable<unknown> {}
get<T>(index: string, schema: JSONSchema): Observable<T> {}
// Observe
watch(index: string): Observable<unknown> {}
watch<T>(index: string, schema: JSONSchema): Observable<T> {}
// Advanced
size: Observable<number>;
has(index: string): Observable<boolean> {}
keys(): Observable<string> {}
}Note: there is also a LocalStorage service available,
but only for compatibility with old versions of this lib.
let user: User = { firstName: 'Henri', lastName: 'Bergson' };
this.storage.set('user', user).subscribe(() => {});You can store any value, without worrying about serializing. But note that:
- storing
nullorundefinedmakes no sense and can cause issues in some browsers, so the item will be removed instead, - you should stick to JSON data, ie. primitive types, arrays and literal objects.
Date,Map,Set,Bloband other special structures can cause issues in some scenarios. See the serialization guide for more details.
To delete one item:
this.storage.delete('user').subscribe(() => {});To delete all items:
this.storage.clear().subscribe(() => {});To get the current value:
this.storage.get('user').subscribe((user) => {
console.log(user);
});Not finding an item is not an error, it succeeds but returns undefined:
this.storage.get('notexisting').subscribe((data) => {
data; // undefined
});Note you will only get one value: the Observable is here for asynchrony but
is not meant to emit again when the stored data is changed.
If you need to watch the value, see the watching guide.
Don't forget it's client-side storage: always check the data, as it could have been forged.
You can use a JSON Schema to validate the data.
this.storage.get('test', { type: 'string' }).subscribe({
next: (user) => { /* Called if data is valid or `undefined` */ },
error: (error) => { /* Called if data is invalid */ },
});See the full validation guide to see how to validate all common scenarios.
You DO NOT need to unsubscribe: the Observable autocompletes (like in the Angular HttpClient service).
But you DO need to subscribe, even if you don't have something specific to do after writing in storage
(because it's how RxJS Observables work).
As usual, it's better to catch any potential error:
this.storage.set('color', 'red').subscribe({
next: () => {},
error: (error) => {},
});For read operations, you can also manage errors by providing a default value:
import { of } from 'rxjs';
import { catchError } from 'rxjs/operators';
this.storage.get('color').pipe(
catchError(() => of('red')),
).subscribe((result) => {});See the errors guide for some details about what errors can happen.
This lib, as native localStorage and indexedDb, is about persistent storage.
Wanting temporary storage (like sessionStorage) is a very common misconception:
an application doesn't need that. More details here.
In addition to the classic localStorage-like API,
this lib also provides a Map-like API for advanced operations:
.keys().has(key).size
See the documentation for more info and some recipes. For example, it allows to implement a multiple databases scenario.
This lib supports the same browsers as Angular. See the browsers support guide for more details and special cases (like private browsing).
If you have multiple apps on the same subdomain and you don't want to share data between them, see the prefix guide.
For interoperability when mixing this lib with direct usage of native APIs or other libs like localForage
(which doesn't make sense in most cases),
see the interoperability documentation.
MIT
Thanks goes to these wonderful people (emoji key):
 Omkar kulkarni 💻 |
This project follows the all-contributors specification. Contributions of any kind welcome!