Redux Thunk

title: Redux Thunk

Redux Thunk

Redux Thunk is middleware that allows you to return functions, rather than just actions, within Redux1. This allows for delayed actions, including working with promises.

The reason we use this middleware is for the reason that not all the actions we perform will be synchronus and some are bound to be non synchronous, like using axios to send a GET request. This will take a bit of time and simple redux does not take into to account this behaviour. So, Redux Thunk comes to the rescue by allowing us to dispatch actions asynchronously, so that we can allow these promises to get resolved.

Example 1:

const INCREMENT_COUNTER = 'INCREMENT_COUNTER'; function increment() { return { type: INCREMENT_COUNTER }; } function incrementAsync() { return dispatch => { setTimeout(() => { // Yay! Can invoke sync or async actions with `dispatch` dispatch(increment()); }, 1000); }; }

Example 2:

const GET_CURRENT_USER = 'GET_CURRENT_USER'; const GET_CURRENT_USER_SUCCESS = 'GET_CURRENT_USER_SUCCESS'; const GET_CURRENT_USER_FAILURE = 'GET_CURRENT_USER_FAILURE'; const getUser = () => { return (dispatch) => { //nameless functions // Initial action dispatched dispatch({ type: GET_CURRENT_USER }); // Return promise with success and failure actions return axios.get('/api/auth/user').then( user => dispatch({ type: GET_CURRENT_USER_SUCCESS, user }), err => dispatch({ type: GET_CURRENT_USER_FAILURE, err }) ); }; };

Installation and Setup

Redux Thunk can be installed using npm install redux-thunk --save or yarn add redux-thunk with the command line. Because it is a Redux tool, you will also need to have Redux set up. Once installed, it is enabled using applyMiddleware():

import { createStore, applyMiddleware } from 'redux'; import thunk from 'redux-thunk'; import rootReducer from './reducers/index'; const store = createStore( rootReducer, applyMiddleware(thunk) );



  1. Increment Counter example cited from Redux Thunk Documentation, 10/02/2018

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