Redux Saga utils for easier use of sagas on the server and dynamic components


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17Jun 9, 2021May 4, 2018Minified + gzip package size for @nfen/redux-saga-injector in KB


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Redux Saga Injector

Inject sagas using sagas, in a small 3KB package. Automatically queues up and cancels sagas on both the server-side and client-side.

This package is intended to solve issues where sagas need to be injected dynamically, and then cancelled when they're no longer needed i.e. when a user goes to another page in a SPA. It prevents side effects from occuring when sagas use similar actions or logic.

Good for composing components with their needed business logic, such as in the case of using react loadable or react universal component, or only running business logic on a single page.


npm install @nfen/redux-saga-injector
# or
yarn add @nfen/redux-saga-injector

Client Side

Components using the SagaInjector, will automatically run with this saga running on the client-side. Make sure to structure your code so that you're not running the sagaRunner on the server.

import { spawn } from 'redux-saga/effects';
import { sagaRunner } from '@nfen/redux-saga-injector';

export default function* rootSaga() {
    yield spawn( sagaRunner );

Manual Saga Injection

You can have more granular control over the injection and cancellation of sagas by dispatching actions.

The sagas to be injected need some sort of differentiator, so that they can be properly cancelled if needed.

import { runSagas, cancelSagas } from '@nfen/redux-saga-injector/actions';
import { genUID } from '@nfen/redux-saga-injector/utils';
import * as sagas from './sagas';
import store from './store';

const sagasToInject = [ sagas.one, sagas.two, sagas.three ];
const sagasId = genUID();

store.dispatch( runSagas(sagasToInject, sagasId) );

// Do some stuff...

store.dispatch( cancelSagas(sagasId) );

Server Side Rendering

This uses a queue in order to inject sagas for the server. Injected sagas are loaded in and then wait til they either finish, are cancelled, or timeout after 5 seconds.

Setting up

First, update the store with the augmentStore function like so. It adds a couple of methods on the store that's used by the queueing system, and for sagas to automatically cancel.

import { createStore, applyMiddleware } from 'redux';
import createSagaMiddleware from 'redux-saga';
import { augmentStore } from '@nfen/redux-saga-injector';

const sagaMiddleware = createSagaMiddleware();
const store = createStore(/* redux store arguments */);
augmentStoreForSagas( sagaMiddleware, store );

React Router 4 Example

This example utilizes express.js and async/await syntax

const Application = ( {
} )=> (
    <Provider store={store}>
            {/* Your App here */}
            <App />

async function render( req, res ){
    const store = createStore();
    const context = {};

    // Server saga listens for any injected sagas to finish
    const preload = store.runSaga( preloadQueue );

    // Start initial render to start sagas
    // This is a throwaway render
     ReactDOMServer.renderToString( <Application store={store} context={context} req={req} /> } );

    // Finish early if context was defined
    if( context.url ) {
        // End in progress sagas as we'll never finish render
        return res.redirect( 301, context.url );

    // Proceed after preload saga finishes
    await preload.done;

    // Get markup with updated store
    const html = ReactDOMServer.renderToString( <Application store={store} context={context} req={req} /> } );

    // Send page to client
    res.send( html );

React HOC Component

A higher order component is availble and can be used like so. It has two benefits:

  • Keeps track of sagas it injects with a unique id, so many components can inject sagas on the same page (for SSR).
  • Cancels the running sagas automatically when the component unmounts
import { SagaInjector } from '@nfen/redux-saga-injector/components';
import MyComponent from './MyComponent';
import * as saga from './sagas';

const injector = SagaInjector({
    sagas: [

export default injector( MyComponent );

Use HOC with react-redux-injector

By utilizing our sister package, you can dynamically inject reducers and sagas on the fly.

import { compose } from 'redux';
import { SagaInjector } from '@nfen/redux-saga-injector/components';
import { ReducerInjector } from '@nfen/redux-reducer-injector/components';
import MyComponent from './MyComponent';
import * as saga from './sagas';
import * as reducers from './reducers';

const injector = (options) => compose(

export default injector( MyComponent );

If you find any bugs or have a feature request, please open an issue on github!

The npm package download data comes from npm's download counts api and package details come from npms.io.