ngrx-store-localstorage

Simple syncing between ngrx store and local or session storage.

Dependencies

ngrx-store-localstorage depends on @ngrx/store and Angular 20+.

Usage

npm install ngrx-store-localstorage --save

1. Wrap localStorageSync in an exported function.
2. Include in your meta-reducers array in StoreModule.forRoot.

import { NgModule } from "@angular/core";
import { BrowserModule } from "@angular/platform-browser";
import {
  StoreModule,
  ActionReducerMap,
  ActionReducer,
  MetaReducer,
} from "@ngrx/store";
import { localStorageSync } from "ngrx-store-localstorage";
import { reducers } from "./reducers";

const reducers: ActionReducerMap<IState> = { todos, visibilityFilter };

export function localStorageSyncReducer(
  reducer: ActionReducer<any>,
): ActionReducer<any> {
  return localStorageSync({ keys: ["todos"] })(reducer);
}
const metaReducers: Array<MetaReducer<any, any>> = [localStorageSyncReducer];

@NgModule({
  imports: [BrowserModule, StoreModule.forRoot(reducers, { metaReducers })],
})
export class MyAppModule {}

API

localStorageSync(config: LocalStorageConfig): Reducer

Provide state (reducer) keys to sync with local storage. Returns a meta-reducer.

Arguments

• config An object that matches with the LocalStorageConfig interface, keys is the only required property.

LocalStorageConfig

An interface defining the configuration attributes to bootstrap localStorageSync. The following are properties which compose LocalStorageConfig:

• keys (required) State keys to sync with local storage. The keys can be defined in two different formats:

  • string[]: Array of strings representing the state (reducer) keys. Full state will be synced (e.g. localStorageSync({keys: ['todos']})).

  • object[]: Array of objects where for each object the key represents the state key and the value represents custom serialize/deserialize options. This can be one of the following:

    • An array of properties which should be synced. This allows for the partial state sync (e.g. localStorageSync({keys: [{todos: ['name', 'status'] }, ... ]})).

    • A reviver function as specified in the JSON.parse documentation.

    • An object with properties that specify one or more of the following:

      • serialize: A function that takes a state object and returns a plain json object to pass to json.stringify.

      • deserialize: A function that takes that takes the raw JSON from JSON.parse and builds a state object.

      • replacer: A replacer function as specified in the JSON.stringify documentation.

      • space: The space value to pass JSON.stringify.

      • reviver: A reviver function as specified in the JSON.parse documentation.

      • filter: An array of properties which should be synced (same format as the stand-alone array specified above).

      • encrypt: A function that takes a state string and returns an encrypted version of that string. e.g. (state: string) => btoa(state)

      • decrypt: A function that takes a state string and returns a decrypted version of that string. e.g. (state: string) => atob(state)

• rehydrate (optional) boolean: Pull initial state from local storage on startup, this will default to false.

• storage (optional) Storage: Specify an object that conforms to the Web Storage API interface to use, this will default to localStorage.

• removeOnUndefined (optional) boolean: Specify if the state is removed from the storage when the new value is undefined, this will default to false.

• storageKeySerializer (optional) (key: string) => string: Custom serialize function for storage keys, used to avoid Storage conflicts.

• restoreDates (boolean? = true): Restore serialized date objects. If you work directly with ISO date strings, set this option to false.

• syncCondition (optional) (state) => boolean: When set, sync to storage medium will only occur when this function returns a true boolean. Example: (state) => state.config.syncToStorage will check the state tree under config.syncToStorage and if true, it will sync to the storage. If undefined or false it will not sync to storage. Often useful for "remember me" options in login.

• checkStorageAvailability (boolean? = false): Specify if the storage availability checking is expected, i.e. for server side rendering / Universal.

• mergeReducer (optional) (state: any, rehydratedState: any, action: any) => any: Defines the reducer to use to merge the rehydrated state from storage with the state from the ngrx store. If unspecified, defaults to performing a full deepmerge on an INIT_ACTION or an UPDATE_ACTION.

Usage

Key Prefix

localStorageSync({
  keys: ["todos", "visibilityFilter"],
  storageKeySerializer: (key) => `cool_${key}`,
});

In above example Storage will use keys cool_todos and cool_visibilityFilter keys to store todos and visibilityFilter slices of state). The key itself is used by default - (key) => key.

Target Depth Configuration

localStorageSync({
  keys: [
    { feature1: [{ slice11: ["slice11_1"], slice14: ["slice14_2"] }] },
    { feature2: ["slice21"] },
  ],
});

In this example, feature1.slice11.slice11_1, feature1.slice14.slice14_2, and feature2.slice21 will be synced to localStorage.feature1 and localStorage.feature2.

Known Workarounds

1. Sync state across multiple tabs

Release Notes / Changelog

From version 10 onwards, check GitHub Releases for release notes. For older versions check the CHANGELOG.md.

Contributing

See CONTRIBUTING.md for instructions on how to contribute.