redux-state-sync

Redux-State-Sync 2.0

A lightweight middleware to sync your redux state across browser tabs. It will listen to the Broadcast Channel and dispatch exactly the same actions dispatched in other tabs to keep the redux state in sync.

Why Redux-State-Sync 2.0?

In redux state sync 1.0, communicate between tabs are fully rely on local storage which means the actions send to other tabs are actually saved in the local storage. We also need to use JSON.stringify and JSON.parse while we saving or retrieving it and all localStorage calls are synchronous. All of this could cause performance problems.

Thanks to BroadcastChannel, we now have a more efficient way to communicate between tabs instead of using any type of local storage. However, Not all the browsers support BroadcastChannel API for now. So I used pubkey's BroadcastChannel to find the best way to communicate between tabs for redux-state-sync 2.0. BroadcastChannel will make sure that the communication between tabs always works.

How to install

Install with npm.

npm install --save redux-state-sync

Install with yarn

yarn add redux-state-sync

TypeScript support

Install with npm.

npm install --save-dev @types/redux-state-sync

Install with yarn

yarn add --dev @types/redux-state-sync

Types are defined here

How to use

Create the state sync middleware with config:

import { createStore, applyMiddleware } from 'redux'
import { createStateSyncMiddleware } from 'redux-state-sync';

const config = {
  // TOGGLE_TODO will not be triggered in other tabs
  blacklist: ['TOGGLE_TODO'],
}
const middlewares = [
  createStateSyncMiddleware(config),
];
 
const store = createStore(rootReducer, {}, applyMiddleware(...middlewares));

Init new tabs with existing state:

1. Use initStateWithPrevTab to get existing state from other tabs

import { createStore, applyMiddleware } from 'redux'
import { createStateSyncMiddleware, initStateWithPrevTab } from 'redux-state-sync';

const config = {
  // TOGGLE_TODO will not be triggered in other tabs
  blacklist: ['TOGGLE_TODO'],
}
const middlewares = [
  createStateSyncMiddleware(config),
];
 
const store = createStore(rootReducer, {}, applyMiddleware(...middlewares));
// init state with other tabs
initStateWithPrevTab(store);

1. Wrap your root reducer with withReduxStateSync

import { withReduxStateSync } from 'redux-state-sync'
 
const rootReducer = combineReducers({
  todos,
  visibilityFilter
})

export default withReduxStateSync(rootReducer)

Note: ignore this if you are using redux-persist, because you will always inite your app with the state in the storage. However, if you don't want to persist the state in the storage and still want to init new tabs with opening tabs' state, you can follow the example above.

Config

channel

Unique name for Broadcast Channel

type: String

default: "redux_state_sync"

const config = {
  channel: 'my_broadcast_channel',
}
const middlewares = [
  createStateSyncMiddleware(config),
];

predicate

A function to let you filter the actions as you wanted.

type: Function

default: null

const config = {
  // All actions will be triggered in other tabs except 'TOGGLE_TODO'
  predicate: actionType => actionType !== 'TOGGLE_TODO'
}
const middlewares = [
  createStateSyncMiddleware(config),
];

blacklist

A list of action types that you don't want to be triggered in other tabs.

type: ArrayOf(<String>)

default: []

const config = {
  // All actions will be triggered in other tabs except 'TOGGLE_TODO'
  blacklist: ['TOGGLE_TODO']
}
const middlewares = [
  createStateSyncMiddleware(config),
];

whitelist

Only actions in this list will be triggered in other tabs.

type: ArrayOf(<String>)

default: []

const config = {
  // Only 'TOGGLE_TODO' will be triggered in other tabs
  whitelist: ['TOGGLE_TODO']
}
const middlewares = [
  createStateSyncMiddleware(config),
];

Warning: You should only use one of the option to filter your actions. if you have all 3 options predicate, blacklist, and whitelist, only one will be effective and the priority is predicate > blacklist > whitelist.

broadcastChannelOption

Redux-state-sync is using BroadcastChannel to comunicate between tabs. broadcastChannelOption is the option passed to broadcastChannel when we creating the channel.

type: Object

default: null

const config = {
  // Only 'TOGGLE_TODO' will be triggered in other tabs
  whitelist: ['TOGGLE_TODO'],
  // enforce a type, oneOf['native', 'idb', 'localstorage', 'node']
  broadcastChannelOption: { type: 'localstorage' },
}
const middlewares = [
  createStateSyncMiddleware(config),
];

prepareState

Prepare state for sending to channel. Will be helpful when using Immutable.js

type: Function

default: state => state

const config = {
  // Map immutable object to js
  prepareState: state => state.toJS()
}
const middlewares = [
  createStateSyncMiddleware(config),
];