React.createElement: type is invalid -- expected a string, but got: object

Question

I've just upgraded to Webpack 2.2 today and have been reading through their guides, which are still a work in progress it seems.

I am having difficulties setting up my application to use webpack-dev-server with hot module reloading.

The guide I was following via the webpack documentation is here, but I am having to modify it to work with a development/production application.

https://webpack.js.org/guides/hmr-react/

The two errors I get are the following...

Uncaught Error: _registerComponent(...): Target container is not a DOM element.
    at invariant (eval at <anonymous> (index.js:2), <anonymous>:44:15)
    at Object._renderNewRootComponent (eval at <anonymous> (index.js:64), <anonymous>:311:44)
    at Object._renderSubtreeIntoContainer (eval at <anonymous> (index.js:64), <anonymous>:401:32)
    at render (eval at <anonymous> (index.js:64), <anonymous>:422:23)
    at hotRenderer (eval at <anonymous> (index.js:73), <anonymous>:41:28)
    at eval (eval at <anonymous> (index.js:73), <anonymous>:47:5)
    at eval (eval at <anonymous> (index.js:73), <anonymous>:54:5)
    at Object.<anonymous> (index.js:73)
    at e (index.js:1)
    at Object.<anonymous> (index.js:146)

AND

Warning: React.createElement: type is invalid -- expected a string (for built-in components) 
or a class/function (for composite components) but got: object.
printWarning    @   warning.js?8a56:36
warning @   warning.js?8a56:60
createElement   @   ReactElementValidator.js?a599:171
hotRenderer @   index.js?2018:30
(anonymous) @   index.js?2018:35
(anonymous) @   index.js?2018:25
(anonymous) @   index.js:73
e   @   index.js:1
(anonymous) @   index.js:146
e   @   index.js:1
(anonymous) @   index.js:1
(anonymous) @   index.js:1

I believe the problem might lie with the fact that my app file is exporting a Component composed of a Redux Provider wrapping a React Router Router.

Here are the two culprit files:

index.js

import './lib/styles.css'
import React from 'react'
import { render } from 'react-dom'

import App from './App'

if (process.env.NODE_ENV === 'development') {
  const { AppContainer } = require('react-hot-loader')
  const hotRender = (Component) => {
    render(
      <AppContainer>
        <Component/>
      </AppContainer>,
      document.getElementById('root')
    )
  }

  hotRender(App)

  if (module.hot) {
    module.hot.accept('./App', () => {
      const NewApp = require('./App').default
      hotRender(NewApp)
    })
  }
} else {
  render(App, document.getElementById('app'))
}

App.js

import React from 'react'
import { Provider } from 'react-redux'
import { createStore } from 'redux'
import store from './redux/store'

import { Router, hashHistory } from 'react-router'
import routes from './routes'

let s = createStore(store,
  process.env.NODE_ENV === 'development' ? (
    window.__REDUX_DEVTOOLS_EXTENSION__ &&
    window.__REDUX_DEVTOOLS_EXTENSION__()
  ) : null
)

const App = () => (
  <Provider store={s}>
    <Router history={hashHistory} routes={routes} />
  </Provider>
)


export default App

If you would like to examine the entire PR that has the changes, that would be awesome! The code is located here: https://github.com/awitherow/aether/pull/64/files

I apologise for some of the CSS changes that slipped into the PR as well, but all of the Webpack 2.2 and later upgrades that I have done in here are related potentially!

EDIT

I have attempted some fixes, simple ones at that... but they are not solving anything.

1. X Wrapping the App in a div, so that it would somehow think it was a DOM element.
2. X exporting App as a class extending Component

Answer 1

Which version of React Router are you using? I was also getting the Warning: React.createElement error in the console, but switching from version 3.0.2 to the 4.0.0-alpha.6 pre-release got rid of it for me.