@ngrx-addons/sync-state

The library for synchronizing state in ngrx between multiple tabs/iframes/windows. Highly inspired by elf-sync-state.

Supported versions

• angular 18+
• @ngrx/store 18+

Installation

npm i @ngrx-addons/sync-state

or

yarn add @ngrx-addons/sync-state

Usage

The module gives ability to sync some of the app’s states using Broadcast Channel API. It supports both root and feature states. The only thing you need to do is to add SyncStateModule.forRoot/provideSyncStore to your AppModule and SyncStateModule.forFeature/provideSyncState to your feature module.

For root states

import { NgModule } from '@angular/core';
import { StoreModule } from '@ngrx/store';
import { BeforeAppInit } from '@ngrx-addons/common';
import { SyncStateModule } from '@ngrx-addons/sync-store';

const counterReducer = ...;
const reducers = {
  counter: counterReducer,
} as const;

@NgModule({
  imports: [
    StoreModule.forRoot(reducers),
    // type provided for hints on states
    SyncStateModule.forRoot<typeof reducers>({
      states: [
        {
          key: 'counter',
          // optional options (default values)
          runGuard: () =>
            typeof window !== 'undefined' &&
            typeof window.BroadcastChannel !== 'undefined',
          source: (state) => state,
          channel: `${channelPrefix}-${key}@store`,
          skip: 1
        },
        // next states to sync, same reducer key can be
        // specified multiple times to sync parts of the state
        // using different channels
      ],
      // optional root options (for all, also feature states)
      channelPrefix: 'some-prefix',
      // optional sync strategy
      strategy: BeforeAppInit, // or AfterAppInit
    }),
  ],
})
export class AppModule {}

or in case of using standalone API:

import { NgModule } from '@angular/core';
import { provideStore } from '@ngrx/store';
import { BeforeAppInit } from '@ngrx-addons/common';
import { provideSyncStore } from '@ngrx-addons/sync-store';

const counterReducer = ...;
const reducers = {
  counter: counterReducer,
} as const;

@NgModule({
  providers: [
    provideStore(reducers),
    // type provided for hints on states
    provideSyncStore<typeof reducers>({
      states: [
        {
          key: 'counter',
          // optional options (default values)
          runGuard: () =>
            typeof window !== 'undefined' &&
            typeof window.BroadcastChannel !== 'undefined',
          source: (state) => state,
          channel: `${channelPrefix}-${key}@store`,
          skip: 1
        },
        // next states to sync, same reducer key can be
        // specified multiple times to sync parts of the state
        // using different channels
      ],
      // optional root options (for all, also feature states)
      channelPrefix: 'some-prefix',
      // optional sync strategy
      strategy: BeforeAppInit, // or AfterAppInit
    }),
  ],
})
export class AppModule {}

The forRoot/provideSyncStore method accepts an object with the following properties:

• states - array of states configs (defined below, required)
• channelPrefix - prefix for all channels (optional)
• strategy - defines if sync actions should be allowed before or only after app initialization (optional, default: BeforeAppInit)

Each state can be described by multiple state configs with the following properties:

• key - the reducer key in app state (required).
• source: a method that receives the observable of a state and return what to save from it (by default - the entire state).
• channel: the name under which the store state is synchronized (by default - the prefix plus store name plus a @store suffix).
• runGuard - returns whether the actual implementation should be run. The default is typeof window !== 'undefined' && typeof window.BroadcastChannel !== 'undefined'
• skip - The number of state changes skipped before the state is synced. Used to skip the initial state change. The default is 1.

For feature states

Remember to add features only once, in any case only the last registration will be used.

import { NgModule } from '@angular/core';
import { StoreModule } from '@ngrx/store';
import { SyncStateModule } from '@ngrx-addons/sync-store';

interface CounterState {
  count: number;
}
const counterReducer = ...;

@NgModule({
  imports: [
    StoreModule.forRoot(),
    // forRoot should be always called, similar to ngrx StoreModule and it's forFeature implementation.
    SyncStateModule.forRoot(),
  ],
})
export class AppModule {}

@NgModule({
  imports: [
    StoreModule.forFeature('counter', reducer),
    // type provided for hints on states
    SyncStateModule.forFeature<CounterState>({
      key: 'counter',
      states: [
        {
          // The same options as for root states, except the key
        },
      ],
    }),
  ],
})
export class CounterModule {}

or in case of using standalone API:

import { NgModule } from '@angular/core';
import { provideStore, provideState } from '@ngrx/store';
import { provideSyncStore, provideSyncState, } from '@ngrx-addons/sync-store';

interface CounterState {
  count: number;
}
const counterReducer = ...;

@NgModule({
  providers: [
    provideStore(),
    // forRoot should be always called, similar to ngrx StoreModule and it's forFeature implementation.
    provideSyncStore(),
  ],
})
export class AppModule {}

@NgModule({
  imports: [
    provideState('counter', reducer),
    // type provided for hints on states
    provideSyncState<CounterState>({
      key: 'counter',
      states: [
        {
          // The same options as for root states, except the key
        },
      ],
    }),
  ],
})
export class CounterModule {}

The forFeature/provideSyncState method accepts an object with the following properties:

• key - the feature key (required)
• states - array of states configs as in forRoot, except key property (required)

Once the state is synchronized, the action (storeSyncAction, type: @ngrx-addons/sync-state/sync) with the proper features is dispatched (multiple times). You can use it to react in effects or meta-reducers.

Excluding/Including keys from the state​

The excludeKeys()/includeKeys() operator can be used to exclude keys from the state:

import { NgModule } from '@angular/core';
import { StoreModule } from '@ngrx/store';
import { excludeKeys, includeKeys } from '@ngrx-addons/common';
import { SyncStateModule } from '@ngrx-addons/sync-store';

const counterReducer = ...;
const reducers = {
  counter: counterReducer,
} as const;

@NgModule({
  imports: [
    StoreModule.forRoot(reducers),
    SyncStateModule.forRoot<typeof reducers>({
      states: [
        {
          key: 'counter',
          source: (state) => state.pipe(excludeKeys(['a', 'b'])),
          // source: (state) => state.pipe(includeKeys(['a', 'b'])),
        },
      ],
    }),
  ],
})
export class AppModule {}

Examples

Check apps