React.createElement: type is invalid -- expected a string

Question

Trying to get react-router (v4.0.0) and react-hot-loader (3.0.0-beta.6) to play nicely, but getting the following error in the browser console:

Warning: React.createElement: type is invalid -- expected a string
(for built-in components) or a class/function (for composite
components) but got: undefined. You likely forgot to export your
component from the file it's defined in.

index.js:

import React from 'react';
import ReactDom from 'react-dom';
import routes from './routes.js';
require('jquery');
import 'bootstrap/dist/css/bootstrap.min.css';
import 'bootstrap/dist/js/bootstrap.min.js';
import './css/main.css';

const renderApp = (appRoutes) => {
    ReactDom.render(appRoutes, document.getElementById('root'));
};

renderApp( routes() );

routes.js:

import React from 'react';
import { AppContainer } from 'react-hot-loader';
import { Router, Route, browserHistory, IndexRoute } from 'react-router';
import store from './store/store.js';
import { Provider } from 'react-redux';
import App from './containers/App.jsx';
import Products from './containers/shop/Products.jsx';
import Basket from './containers/shop/Basket.jsx';

const routes = () => (

    <AppContainer>
        <Provider store={store}>
            <Router history={browserHistory}>
                <Route path="/" component={App}>
                    <IndexRoute component={Products} />
                    <Route path="/basket" component={Basket} />
                </Route>
            </Router>
        </Provider>
    </AppContainer>

);

export default routes;

Answer 1

Most of the time this is due to an incorrect export/import.

Common error:

// File: LeComponent.js
export class LeComponent extends React.Component { ... }

// File: App.js
import LeComponent from './LeComponent';

Possible option:

// File: LeComponent.js 
export default class LeComponent extends React.Component { ... }

// File: App.js
import LeComponent from './LeComponent';

There are a few ways it could be wrong, but that error is because of an import/export mismatch 60% of the time, everytime.

Edit

Typically you should get a stacktrace that indicates an approximate location of where the failure occurs. This generally follows straight after the message you have in your original question.

If it doesn't show, it might be worth investigating why (it might be a build setting that you're missing). Regardless, if it doesn't show, the only course of action is narrowing down where the export/import is failing.

Sadly, the only way to do it, without a stacktrace is to manually remove each module/submodule until you don't get the error anymore, then work your way back up the stack.

Edit 2

Via comments, it was indeed an import issue, specifically importing a module that didn't exist

Answer 2

I was getting this error as well.

I was using:

import BrowserRouter from 'react-router-dom';

Fix was doing this, instead:

import { BrowserRouter } from 'react-router-dom';

Answer 3

Try this

npm i react-router-dom@next

in your App.js

import { BrowserRouter as Router, Route } from 'react-router-dom'

const Home = () => <h1>Home</h1>

const App = () =>(
  <Router>
    <Route path="/" component={Home} />
  </Router>
)

export default App;

Answer 4

Array of components

A common way to get this error is using an array of components, with a positional index used to select the component to render from the array. I saw a code like this many times:

const checkoutSteps = [Address, Shipment, Payment]

export const Checkout = ({step}) => {

  const ToRender = checkoutSteps[step]

  return (
    <ToRender />
  )
}

This is not necessary bad code, but if you call it with a wrong index (eg -1, or 3 in this case), the ToRender component will be undefined, throwing the React.createElement: type is invalid... error:

<Checkout step={0} /> // <Address />
<Checkout step={1} /> // <Shipment />
<Checkout step={2} /> // <Payment />
<Checkout step={3} /> // undefined
<Checkout step={-1} /> // undefined

A rational solution

You should protect yourself and your collegues from this hard-to-debug code using a more explicit approach, avoiding magic numbers and using PropTypes:

const checkoutSteps = {
  address: Address,
  shipment Shipment,
  payment: Payment
}

const propTypes = {
  step: PropTypes.oneOf(['address', 'shipment', 'payment']),
}

/* TIP: easier to maintain
const propTypes = {
  step: PropTypes.oneOf(Object.keys(checkoutSteps)),
}
*/

const Checkout = ({step}) => {

  const ToRender = checkoutSteps[step]

  return (
    <ToRender />
  )
}

Checkout.propTypes = propTypes

export default Checkout

And your code will look like this:

// OK
<Checkout step="address" /> // <Address />
<Checkout step="shipment" /> // <Shipment />
<Checkout step="payment" /> // <Payment />

// Errors
<Checkout step="wrongstep" /> // explicit error "step must be one of..."
<Checkout step={3} /> // explicit error (same as above)
<Checkout step={myWrongVar} /> // explicit error (same as above)

Benefits of this approach

• code is more explicit, you can clearly see what you want to render
• you don't need to remember the numbers and their hidden meaning (1 is for Address, 2 is for...)
• errors are explicit too
• no headache for your peers :)

Answer 5

You need to be aware of named export and default export. See When should I use curly braces for ES6 import?

In my case, I fixed it by changing from

import Provider from 'react-redux'

to

import { Provider } from 'react-redux'

Answer 6

I had this problem when I added a css file to the same folder as the component file.

My import statement was:

import MyComponent from '../MyComponent'

which was fine when there was only a single file, MyComponent.jsx. (I saw this format in an example and gave it a try, then forgot I'd done it)

When I added MyComponent.scss to the same folder, the import then failed. Maybe JavaScript loaded the .scss file instead, and so there was no error.

My conclusion: always specify the file extension even if there is only one file, in case you add another one later.

Answer 7

I was getting this error as well.

I was using:

import ReactDOM from 'react-dom';

Fix was doing this, instead:

import {ReactDOM} from 'react-dom';

Answer 8

For future googlers:

My solution to this problem was to upgrade react and react-dom to their latest versions on NPM. Apparently I was importing a Component that was using the new fragment syntax and it was broken in my older version of React.

Answer 9

This issue has occurred to me when I had a bad reference in my render/return statement. (point to a non existing class). Also check your return statement code for bad references.

Answer 10

Most of the time this indicates an import/export error. But be careful to not only make sure the referenced file in the stack trace is well exported itself, but also that this file is importing other components correctly. In my case the error was like this:

import React from 'react';

// Note the .css at the end, this is the cause of the error!
import SeeminglyUnimportantComponent from './SeeminglyUnimportantComponent.css';

const component = (props) => (            
  <div>
    <SeeminglyUnimportantComponent />
    {/* ... component code here */}
  </div>    
);

export default component;

Answer 11

I think the most important thing to realize when troubleshooting this bug is that it manifests when you attempt to instantiate a component that doesn't exist. This component doesn't have to be imported. In my case I was passing components as properties. I forgot to update one of the calls to properly pass the component after some refactoring. Unfortunately, since JS isn't statically typed my bug wasn't caught, and it took some time to figure out what was happening.

To troubleshoot this bug inspect the component before you render it, to make sure that it's the type of component you expect.

Answer 12

It means your import/export is incorrect.

• Check newly added import/exports.
• In my case I was using curly brackets unnecessary. Issue got resolved automatically when I removed these curly brackets.

import { OverlayTrigger } from 'react-bootstrap/OverlayTrigger';

Answer 13

In my case, VS Code let me down.

Here is the hierarchy of my components:

<HomeScreen> =>  <ProductItemComponent> =>  <BadgeProductComponent>

I had the wrong import of the ProductItemComponent. The fact is that this component used to be in the shared folder, but then it was moved to the home folder. But when I moved the file to another folder, the import did not update and remained the same:

../shared/components

At the same time, the component worked fine and VS Code did not highlight the error. But when I added a new BadgeProductComponent to the ProductItemComponent, I had a Render Error and thought that the problem was in the new BadgeProductComponent, because when this component was removed, everything worked!

And even more than that, if I went through a hotkey to the ProductItemComponent which had the ../shared/components address, then VS Code redirected me to the Home folder with the address ../home/components.

In general, check the correctness of all imports at all component levels.

Answer 14

I was missing a React Fragment:

function Bar({ children }) {

  return (
    <div>
     {children}
    </div>
  );
}

function Foo() {
  return (
    <Bar>
      <Baz/>
      <Qux/>
    </Bar>
  );
}

The code above throws the error above. But this fixes it:

<Bar>
  <>
    <Baz/>
    <Qux/>
  </>
</Bar>

Answer 15

My case was not an import issue like many of the answers above say. In mine we were using a wrapper component to do some translation logic and I was passing the child component in incorrectly like so:

const WrappedComponent = I18nWrapper(<ChildForm {...additionalProps} />);

When I should have been passing it in as a function:

const WrappedComponent = I18nWrapper(() => <ChildForm {...additionalProps} />);

Answer 16

What missing for me was I was using

import { Router, Route, browserHistory, IndexRoute } from 'react-router';

instead or correct answer should be :

import { BrowserRouter as Router, Route } from 'react-router-dom';

Ofcourse you need to add npm package react-router-dom:

npm install react-router-dom@next --save

Answer 17

If you have this error when testing a component, make sure that every child component render correctly when run alone, if one of your child component depend on external resources to render, try to mock it with jest or any other mocking lib:

Exemple:

jest.mock('pathToChildComponent', () => 'mock-child-component')

Answer 18

In my case, the error occurred when trying to use ContextApi. I have mistakenly used:

const MyContext = () => createContext()

But it should have been defined as:

const MyContext = createContext()

I am posting it here so that future visitors who get stuck on such a silly mistake will get it helpful to avoid hours of headache, coz this is not caused by incorrect import/export.

Answer 19

Circular dependency is also one of the reasons for this. [in general]

Answer 20

In my case I forgot to import and export my (new) elements called by the render in the index.js file.

Answer 21

It's quite simple, really. I got this issue when I started coding React, and the problem is almost always because the import:

import React, { memo } from 'react';

You can use destructuring this because react lib has a property as memo, but you can not destructuring something like this

import { user } from 'assets/images/icons/Profile.svg';

because it's not a object.

Hope it helps!

Answer 22

xxxxx.prototype = {
  dxxxx: PropTypes.object.isRequired, // eslint-disable-line react/forbid-prop-types
};

You must add // eslint-disable-line react/forbid-prop-types, then it work!

Answer 23

The application that I was working on, stored the name of react components as a widget configuration in the browser storage. Some of these components got deleted and the app was still trying to render them. By clearing the browser cache, I was able to resolve my issue.

Answer 24

For me, I had two files with the same name but different extensions (.js and .tsx). Thus in my import I had to specify the extension.

Answer 25

For me removing Switch solved the issue

import React from "react";
import "./styles.css";
import { Route, BrowserRouter, Routes } from "react-router-dom";
import LoginPage from "./pages/LoginPage";
import HomePage from "./pages/HomePage";

export default function App() {
  return (
    <BrowserRouter>
      <Routes>
        <Route exact path="/" element={<HomePage />} />
        <Route path="/login" element={<LoginPage />} />
      </Routes>
    </BrowserRouter>
  );
}

Answer 26

For me this happened while I have tried to import a named import as default import, SO I got this error

import ProductCard from '../../../components/ProductCard' // that what caused the issue

Error: Element type is invalid: expected a string (for built-in components) or a class/function (for composite components) but got: undefined. You likely forgot to export your component from the file it's defined in, or you might have mixed up default and named imports.

Check the render method of `TopVente`.

So I had to fix it by name import

import { ProductCard } from '../../../components/ProductCard'

Answer 27

In my case, the order in which you create the component and render, mattered. I was rendering the component before creating it. The best way is to create the child component and then the parent components and then render the parent component. Changing the order fixed the issue for me.

Answer 28

In my case I just had to upgrade from react-router-redux to react-router-redux@next. I'm assuming it must have been some sort of compatibility issue.

Answer 29

I was getting this error and none of the responses was my case, it might help someone googling:

I was defining a Proptype wrong:

ids: PropTypes.array(PropTypes.string)

It should be:

ids: PropTypes.arrayOf(PropTypes.string)

VSCode and the compile error didnt give me a correct hint.

Answer 30

In simply words, somehow the following is happening:

render() {
    return (
        <MyComponent /> // MyComponent is undefined.
    );
}

It may not necessarily be related with some incorrect import or export:

render() {
    // MyComponent may be undefined here, for example.
    const MyComponent = this.wizards[this.currentStep];

    return (
        <MyComponent />
    );
}