A simple state container and express middlware wrapper (redux like)

middleware.js

const React = require('react')
const ReactDOM = require('react-dom')
const createStore = require('./state-container')

module.exports = storeMiddleware
function storeMiddleware (reducer, initialState, Component) {
  let _c = Component
  if (_c && !_c.hasOwnProperty('$$typeof')) {
    _c = React.createFactory(Component)
  }

  return function (req, res, next) {
    // Create the store
    const store = createStore(reducer, initialState)
    res.locals.store = store

    // Override render method
    res.render = function renderComponent (Comp) {
      let __c = Comp || _c
      if (!__c.hasOwnProperty('$$typeof')) {
        __c = React.createFactory(__c)
      }

      let el = document.getElementById('app')
      ReactDOM.render(__c(store.getState()), el)

      store.subscribe(() => {
        ReactDOM.render(__c(store.getState()), el)
      })
    }

    next()
  }
}

state-container.js

module.exports = createStore
function createStore (reducer, initialState) {
  let state = initialState
  const listeners = []

  function dispatch (action) {
    if (typeof action === 'function') {
      return action(dispatch)
    }
    if (typeof action.then === 'function') {
      return action.then(dispatch, dispatch)
    }

    let _s = state
    state = reducer(state, action)

    // Call subscribers
    listeners.forEach((listener) => listener(state, _s, action))

    return action
  }

  function subscribe (listener) {
    let subscribed = true
    listeners.push(listener)
    return () => {
      if (!subscribed) {
        return
      }
      subscribed = false
      listeners.splice(listeners.indexOf(listener), 1)
    }
  }

  function getState () {
    return state
  }

  return { dispatch, subscribe, getState }
}