redux middleware; sagas for thunks

Usage no npm install needed!

<script type="module">
  import reduxCosed from '';


redux-cosed Build Status

Sagas for 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-cosed handle the side-effects, all you need to worry about is describing how the side-effects should look.


  • Don't want the weight of redux-saga (forking model, task cancellation, spawning infinite loops, etc.)
  • Like action creators spawning side-effects
  • Want to describe side-effects as data
  • Testing is incredibly simple
  • Same API as redux-saga (select, put, call, spawn, all, delay)
  • Typescript typings
  • Upgradability from react-cosed and 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-cosed 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-cosed. This is where redux-cosed shines. The function we wrote for react-cosed looks almost identical to the one we use for redux-cosed. The only addition is redux-cosed 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 cosed 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-cosed), upgrade to redux with simple side-effects (redux-cosed), and then upgrade to really complex flow mechanisms (redux-saga).

react-cosed -> redux-cosed -> redux-saga


yarn add redux-cosed


import cosedMiddleware, { createEffect, call, select, put } from 'redux-cosed';
import { applyMiddleware, createStore } from 'redux';

const store = createStore(

// 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


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