Storage

Back your stores with localStorage, sessionStorage or any other mechanism you wish.

Install

The Storage plugin can be installed using NPM:

npm i @ngxs/storage-plugin --S

Usage

Import the NgxsStoragePluginModule into your app module like:

import { NgxsModule } from '@ngxs/store';
import { NgxsStoragePluginModule } from '@ngxs/storage-plugin';

@NgModule({
  imports: [
    NgxsModule.forRoot([]),
    NgxsStoragePluginModule.forRoot()
  ]
})
export class AppModule {}

It is recommended to register the storage plugin before other plugins so initial state can be picked up by those plugins.

Options

The plugin has the following optional values:

• key: Default key to persist. You can pass a string or array of strings that can be deeply nested via dot notation. If not provided, it defaults to all states using the @@STATE key.

• storage: Storage strategy to use. This defaults to LocalStorage but you can pass SessionStorage or anything that implements the StorageEngine API.

• deserialize: Custom deserializer. Defaults to JSON.parse

• serialize: Custom serializer, defaults to JSON.stringify

• migrations: Migration strategies

Custom Storage Engine

You can implement your own storage engine by providing a engine that implements setItem and getItem.

import { NgxsStoragePluginModule, StorageEngine, STORAGE_ENGINE } from '@ngxs/storage-plugin';

export class MyStorageEngine implements StorageEngine {
  getItem(name) {
    // Your logic here
  }

  setItem(key, value) {
    // Your logic here
  }
}

@NgModule({
  imports: [
    NgxsModule.forRoot([]),
    NgxsStoragePluginModule.forRoot()
  ],
  providers: [
    {
      provide: STORAGE_ENGINE,
      useClass: MyStorageEngine
    }
  ]
})
export class MyModule {}

Migrations

You can migrate data from one version to another during the startup of the store. Below is a strategy to migrate my state from animals to newAnimals.

@NgModule({
  imports: [
    NgxsModule.forRoot([]),
    NgxsStoragePluginModule.forRoot({
      migrations: [
        {
          version: 1,
          key: 'zoo',
          versionKey: 'myVersion',
          migrate: (state) => {
            return {
              newAnimals: state.animals,
              version: 2 // Important to set this to the next version!
            }
          }
        }
      ]
    })
  ],
})
export class MyModule {}

In the migration strategy, we define:

• version: The version we are migrating

• versionKey: The identifier for the version key (Defaults to 'version')

• migrate: A function that accepts a state and expects the new state in return.

• key: The key for the item to migrate. If not specified, it takes the entire storage state.

Note: Its important to specify the strategies in the order of which they should progress.