What is the best way to access redux store outside a react component?

Question

Export the store from the module you called createStore with. Then you are assured it will both be created and will not pollute the global window space.

MyStore.js

const store = createStore(myReducer);
export store;

or

const store = createStore(myReducer);
export default store;

MyClient.js

import {store} from './MyStore'
store.dispatch(...)

or if you used default

import store from './MyStore'
store.dispatch(...)

For Multiple Store Use Cases

If you need multiple instances of a store, export a factory function. I would recommend making it async (returning a promise).

async function getUserStore (userId) {
   // check if user store exists and return or create it.
}
export getUserStore

On the client (in an async block)

import {getUserStore} from './store'

const joeStore = await getUserStore('joe')

Found a solution. So I import the store in my api util and subscribe to it there. And in that listener function I set the axios' global defaults with my newly fetched token.

This is what my new api.js looks like:

// tooling modules
import axios from 'axios'

// store
import store from '../store'
store.subscribe(listener)

function select(state) {
  return state.auth.tokens.authentication_token
}

function listener() {
  let token = select(store.getState())
  axios.defaults.headers.common['Authorization'] = token;
}

// configuration
const api = axios.create({
  baseURL: 'http://localhost:5001/api/v1',
  headers: {
    'Content-Type': 'application/json',
  }
})

export default api

Maybe it can be further improved, cause currently it seems a bit inelegant. What I could do later is add a middleware to my store and set the token then and there.

You can use store object that is returned from createStore function (which should be already used in your code in app initialization). Than you can use this object to get current state with store.getState() method or store.subscribe(listener) to subscribe to store updates.

You can even save this object to window property to access it from any part of application if you really want it (window.store = store)

More info can be found in the Redux documentation .

You can use Middleware according to How can I access the store in non react components?:

Middleware

function myServiceMiddleware(myService) {
  return ({ dispatch, getState }) => next => action => {
    if (action.type == 'SOMETHING_SPECIAL') {
      myService.doSomething(getState());
      myService.doSomethingElse().then(result => dispatch({ type: 'SOMETHING_ELSE', result }))
    }
    return next(action);
  }
}

Usage

import { createStore, applyMiddleware } from 'redux'
const serviceMiddleware = myServiceMiddleware(myService)
const store = createStore(reducer, applyMiddleware(serviceMiddleware))

Further Reading: Redux Docs > Middleware

Like @sanchit proposed middleware is a nice solution if you are already defining your axios instance globally.

You can create a middleware like:

function createAxiosAuthMiddleware() {
  return ({ getState }) => next => (action) => {
    const { token } = getState().authentication;
    global.axios.defaults.headers.common.Authorization = token ? `Bearer ${token}` : null;

    return next(action);
  };
}

const axiosAuth = createAxiosAuthMiddleware();

export default axiosAuth;

And use it like this:

import { createStore, applyMiddleware } from 'redux';
const store = createStore(reducer, applyMiddleware(axiosAuth))

It will set the token on every action but you could only listen for actions that change the token for example.