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https://github.com/cyrilletuzi/angular-async-local-storage

Efficient client-side storage for Angular: simple API + performance + Observables + validation
https://github.com/cyrilletuzi/angular-async-local-storage

angular indexeddb javascript localstorage rxjs typescript

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Efficient client-side storage for Angular: simple API + performance + Observables + validation

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# Async local storage for Angular



Efficient client-side storage for Angular:

- **simplicity**: simple API similar to native `localStorage`,

- **perfomance**: internally stored via the asynchronous `indexedDB` API,

- **Angular-like**: wrapped in RxJS `Observable`s,

- **security**: validate data with a JSON Schema or with [`typebox`](https://github.com/sinclairzx81/typebox),

- **compatibility**: works around some browsers issues and heavily tested via GitHub Actions,

- **documentation**: API fully explained, and a changelog!



> [!TIP]

> I am also the author of the [Angular Schematics extension for Visual Studio Code](https://marketplace.visualstudio.com/items?itemName=cyrilletuzi.angular-schematics), installed 1 million times. Feel free to give it a try.



## Why this library?



Angular does not provide a client-side storage service, and almost every app needs some client-side storage. There are 2 native JavaScript APIs available:

- [localStorage](https://developer.mozilla.org/en-US/docs/Web/API/Storage/LocalStorage)

- [indexedDB](https://developer.mozilla.org/en-US/docs/Web/API/IndexedDB_API)



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 is a mess to use:  you will soon be caught by the callback hell, as it does not support `Promise`s.



This library has a simple API similar to native `localStorage`, but internally stores data via the asynchronous `indexedDB` for performance. All of this powered by [RxJS](https://rxjs.dev/).



## Getting started



Install the package:



```bash

# For Angular LTS (Angular >= 16):

ng add @ngx-pwa/local-storage

```



*Done!*



If for any reason `ng add` does not work, follow the [manual installation guide](https://github.com/cyrilletuzi/angular-async-local-storage/blob/main/docs/MANUAL_INSTALLATION.md).



> [!NOTE]

> Angular versions <= 15 are [officially outdated](https://angular.dev/reference/versions).



### Upgrading



To update to new versions, see the **[migration guides](https://github.com/cyrilletuzi/angular-async-local-storage/blob/main/MIGRATION.md).**



## API



```typescript

import { StorageMap } from '@ngx-pwa/local-storage';



@Injectable()

export class YourService {

  constructor(private storage: StorageMap) {}

}

```



This service API is similar to the standard [`Map` API](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map), and close to the standard [`localStorage` API](https://developer.mozilla.org/en-US/docs/Web/API/Storage/LocalStorage).



```typescript

class StorageMap {

  // Write

  set(index: string, value: unknown): Observable {}

  delete(index: string): Observable {}

  clear(): Observable {}



  // Read (one-time)

  get(index: string): Observable {}

  get(index: string, schema: JSONSchema): Observable {}



  // Advanced

  watch(index: string): Observable {}

  watch(index: string, schema: JSONSchema): Observable {}

  size: Observable;

  has(index: string): Observable {}

  keys(): Observable {}

}

```



## How to



### Writing data



```typescript

const user: User = { firstName: 'Henri', lastName: 'Bergson' };



this.storage.set('user', user).subscribe(() => {});

```



> [!NOTE]

> You can store any value, without worrying about serializing. But note that:

> - storing `null` or `undefined` makes no sense and can cause issues in some browsers, so the item will be removed instead,

> - you should stick to serializable JSON data, meaning primitive types, arrays and *literal* objects. `Date`, `Map`, `Set`, `Blob` and other special structures can cause issues in some scenarios. Read the [serialization guide](https://github.com/cyrilletuzi/angular-async-local-storage/blob/main/docs/SERIALIZATION.md) for more details.



### Deleting data



To delete one item:

```typescript

this.storage.delete('user').subscribe(() => {});

```



To delete all items:

```typescript

this.storage.clear().subscribe(() => {});

```



### Reading data



To get the *current* value:

```typescript

this.storage.get('user').subscribe((user) => {

  console.log(user);

});

```



Not finding an item is not an error, it succeeds but returns `undefined`:

```typescript

this.storage.get('notexisting').subscribe((data) => {

  data; // undefined

});

```



> [!IMPORTANT]

> 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, read the [watching guide](https://github.com/cyrilletuzi/angular-async-local-storage/blob/main/docs/WATCHING.md).



### Checking data



Do not forget it is client-side storage: **always check the data**, as it could have been forged.



You **should** use a [JSON Schema](http://json-schema.org/) to validate the data.



```typescript

this.storage.get('test', { type: 'string' }).subscribe({

  next: (user) => { /* Called if data is valid or `undefined` */ },

  error: (error) => { /* Called if data is invalid */ },

});

```



> [!TIP]

> Read the [full validation guide](https://github.com/cyrilletuzi/angular-async-local-storage/blob/main/docs/VALIDATION.md) to learn how to validate all common scenarios.



### Subscription



You do *NOT* need to unsubscribe: the `Observable` autocompletes (like in the Angular `HttpClient` service).



But **you *DO* need to subscribe**, even if you do not have something specific to do after writing in storage (because it is how RxJS `Observable`s work).



```typescript

this.storage.set('user', user); // Does nothing

```



### Errors



As usual, it is better to catch any potential error:

```typescript

this.storage.set('color', 'red').subscribe({

  next: () => {},

  error: (error) => {},

});

```



For read operations, you can also manage errors by providing a default value:

```typescript

import { catchError, of } from 'rxjs';



this.storage.get('color').pipe(

  catchError(() => of('red')),

).subscribe((result) => {});

```



> [!TIP]

> Read the [errors guide](https://github.com/cyrilletuzi/angular-async-local-storage/blob/main/docs/ERRORS.md) for some details about what errors can happen.



### Expiration



This lib, as native `localStorage` and `indexedDb`, is about *persistent* storage.



Wanting *temporary* storage (like `sessionStorage`) is a very common misconception: an application does not need that.



> [!TIP]

> Read [the expiration guide](https://github.com/cyrilletuzi/angular-async-local-storage/blob/main/docs/EXPIRATION.md).



### `Map`-like operations



In addition to the classic `localStorage`-like API, this library also provides a `Map`-like API for advanced operations:

  - `.keys()`

  - `.has(key)`

  - `.size`



> [!TIP]

> Read the [Map-like operations guide](https://github.com/cyrilletuzi/angular-async-local-storage/blob/main/docs/MAP_OPERATIONS.md) for more info and some recipes. For example, it allows to implement a multiple databases scenario.



## Support



### Browser support



This library supports [the same browsers as Angular](https://angular.dev/reference/versions#browser-support).



> [!TIP]

Read [the browsers support guide](https://github.com/cyrilletuzi/angular-async-local-storage/blob/main/docs/BROWSERS_SUPPORT.md) for more details and special cases.



### Collision



The library has configurable options if you have multiple apps on the same *sub*domain *and* you do not want to share data between them.



> [!TIP]

> Read the [collision guide](https://github.com/cyrilletuzi/angular-async-local-storage/blob/main/docs/COLLISION.md).



### Interoperability



The library has configurable options for interoperability when mixing this library with direct usage of native APIs or other libraries like `localForage` (which does not make sense in most cases).



> [!TIP]

> Read the [interoperability documentation](https://github.com/cyrilletuzi/angular-async-local-storage/blob/main/docs/INTEROPERABILITY.md).



### Changelog



[Changelog available here](https://github.com/cyrilletuzi/angular-async-local-storage/blob/main/CHANGELOG.md), and [migration guides here](https://github.com/cyrilletuzi/angular-async-local-storage/blob/main/MIGRATION.md).



## License



MIT