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declarative redux middleware for handling side-effects
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redux-cofx Build Status

Redux middleware: Sagas as thunks; redux-saga meets redux-thunk

Middleware for redux that allows developers to dispatch actions which trigger generator functions. On top of that, these generator functions have an API for describing side-effect as opposed to activating them. Let redux-cofx handle the side-effects, all you need to worry about is describing how the side-effects should work.


  • Action creators spawning side-effects
  • Want to describe side-effects as data
  • Testing is incredibly simple
  • Similar API as redux-saga (select, put, take, call, fork, spawn, all, delay)
  • Typescript support
  • Upgradability from react-cofx and to redux-saga

Upgrade plan

Sometimes all we need to do is fetch data from a server and load it into one component. That data lives inside that component and we don't need to share it with anything else. This is where react-cofx shines. However, because requirements change over time, we need to eventually share that data with multiple components and now we need to save the data in redux. We could use redux-thunk to accomplish that goal, but it's difficult to test thunks and the way to fetch the data looks a little different than react-cofx. This is where redux-cofx shines. The function we wrote for react-cofx looks almost identical to the one we use for redux-cofx. The only addition is redux-cofx provides the ability to query redux state and dispatch actions. Sometimes requirements change even more and now we need the ability to listen to multiple events and other more complex flow control mechanisms. This is when we would introduce redux-saga. The cofx API was built with redux-saga in mind. It's the same exact API. All we would need to do is change the import path for call, etc. to redux-saga/effects and it should work exactly the same.

So what do we have? We have an upgrade path to start small (react-cofx), upgrade to redux with simple side-effects (redux-cofx), and then upgrade to really complex flow mechanisms (redux-saga).

react-cofx -> redux-cofx -> redux-saga


yarn add redux-cofx


import cofxMiddleware, { createEffect, call, select, put } from "redux-cofx";
import { applyMiddleware, createStore } from "redux";

const reducer = (state) => state;
const store = createStore(reducer, applyMiddleware(cofxMiddleware));

// action creators
const todosSuccess = payload => ({
  type: "TODO_SUCCESS",
const uploadTodos = todos => createEffect(effect, todos);

// selector
const getApiToken = state => state.token;

// effect
function* effect(todos) {
  const token = yield select(getApiToken);

  const result = yield call(fetch, "/todos", {
    method: "POST",
    headers: {
      Authorization: `Bearer ${token}`
    body: JSON.stringify(todos)
  const json = yield call([result, "json"]);

  yield put(todosSuccess(json));

const todos = ["drop kids off at the pool", "make dinner"];
// trigger effect

Using enableBatching we also provide the ability to batch multiple actions while only triggering one state change. See the API section for more info.


See cofx for instructions on how to test an effect function.


For cofx specific effects (e.g. call, fork, spawn, delay, all), see cofx docs


Accepts a function with state as the parameter

const getToken = (state) => {
  return state.token;

function* effect() {
  const token = yield select(getToken);


alias for store.dispatch

const setToken = (payload) => {
  return {
    type: 'SET_TOKEN',

function* effect() {
  yield put(setToken('1234'));

batch (requires enableBatching, added v2.0)

dispatch multiple actions with only a single state update. This effect takes an array of actions and dispatches them all within a single state update. This is useful if there are multiple actions being dispatched in sequence and you don't want to re-render the view all of those times.

import { batch } from 'redux-cofx';

const setToken = (payload) => {
  return {
    type: 'SET_TOKEN',
const login = () => {
  return {
    type: 'LOGIN',

function* effect() {
  yield batch([
  ]); // this will only trigger one state update and only one re-render of react!


Waits for the action to be dispatched

function* effect() {
  const action = yield take('SOMETHING');

console.log('output ->');
store.dispatch({ type: 'SOMETHING', payload: 'nice!' });

// output ->
// 'nice!'

enableBatching (optional, added v2.0)

This is a higher order reducer that enables the use of batch which allows multiple actions to be dispatched with a single re-render.

import cofxMiddleware, { enabledBatching } from "redux-cofx";
import { applyMiddleware, createStore } from "redux";

const reducer = (state) => state;
const rootReducer = enableBatching(reducer);
const store = createStore(rootReducer, applyMiddleware(cofxMiddleware));


This function creates an effect action that you would dispatch with redux.

import { put, createEffect } from 'redux-cofx';

function* effOne(payload: any) {
  // payload === 'ok'
  yield put({ type: 'AWESOME', payload });

const one = (payload: any) => createEffect(effOne, payload);

cancel an effect (added v2.0)

We also provide the ability to cancel an effect. The cancel must be a promise. When the cancel promise is resolved then it will cancel the effect.

import { put, createEffect } from 'redux-cofx';

function* effOne(payload: any) {
  yield delay(1000); // delay for 1 second
  yield put({ type: 'AWESOME', payload }); // payload === 'ok'

const cancel = () => new Promise((resolve) => {
  setTimeout(() => {
  }, 500);
const one = (payload: any) => createEffect({
  fn: effOne,
  args: [payload],
// the effect will be cancelled before the action can be dispatched!


This is a helper function to create effects based on a map of effect names to effect function. The created effects will accept a payload and send it as a parameter to the effect function.

import { put, createEffects } from 'redux-cofx';

function* effOne(payload: any) {
  // payload === 'ok'
  yield put({ type: 'AWESOME', payload });

function* effTwo(payload: any) {
  // payload === 'nice'
  yield put({ type: 'WOW', payload });

const effects = createEffects({
  one: effOne,
  two: effTwo,

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