Uncaught Error: Invariant Violation: Element type is invalid: expected a string (for built-in components) or a class/function but got: object

I am getting this error:

Uncaught Error: Invariant Violation: Element type is invalid: expected a string (for built-in components) or a class/function (for composite components) but got: object. 

This is my code:

var React = require('react') var ReactDOM = require('react-dom') var Router = require('react-router') var Route = Router.Route var Link = Router.Link var App = React.createClass({ render() { return ( <div> <h1>App</h1> <ul> <li><Link to="/about">About</Link></li> </ul> </div> ) } }) var About = require('./components/Home') ReactDOM.render(( <Router> <Route path="/" component={App}> <Route path="about" component={About} /> </Route> </Router> ), document.body) 

My Home.jsx file:

var React = require('react'); var RaisedButton = require('material-ui/lib/raised-button'); var Home = React.createClass({ render:function() { return ( <RaisedButton label="Default" /> ); }, }); module.exports = Home; 

46 Answers

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In my case (using Webpack) it was the difference between:

import {MyComponent} from '../components/xyz.js'; 

vs

import MyComponent from '../components/xyz.js'; 

The second one works while the first is causing the error. Or the opposite.

you need export default or require(path).default

var About = require('./components/Home').default 

Have you just modularized any of your React components? If yes, you will get this error if you forgot to specify module.exports, for example:

non-modularized previously valid component/code:

var YourReactComponent = React.createClass({ render: function() { ... 

modularized component/code with module.exports:

module.exports = React.createClass({ render: function() { ... 

If you get this error, it might be because you're importing link using

import { Link } from 'react-router'

instead, it might be better to use

 import { Link } from 'react-router-dom' ^--------------^ 

I believe this is a requirement for the react router version 4

In my case, one of the exported child module was not returning a proper react component.

const Component = <div> Content </div>; 

instead of

const Component = () => <div>Content</div>; 

The error shown was for the parent, hence couldn't figure out.

Don't get surprised by the list of answers for a single question. There are various causes for this issue;

For my case, the warning was

warning.js:33 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. Check your code at index.js:13.

Followed by the error

invariant.js:42 Uncaught 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.

I couldn't understand the error since it doesn't mention any method or file name. I was able to resolve only after looking at this warning, mentioned above.

I have the following line at the index.js.

<ConnectedRouter history={history}> 

When I googled for the above error with the keyword "ConnectedRouter" I found the solution in a GitHub page.

The error is because, when we install react-router-redux package, by default we install this one. but not the actual library.

To resolve this error, install the proper package by specifing the npm scope with @

npm install react-router-redux@next 

You don't need to remove the wrongly installed package. It will be automatically overwritten.

Thank you.

PS: Even warning helps you. Don't neglect warning just looking at the error alone.

Router is also one of the properties of react-router. So change your modules require code like that:

 var reactRouter = require('react-router') var Router = reactRouter.Router var Route = reactRouter.Route var Link = reactRouter.Link 

If you want to use ES6 syntax the link use(import), use babel as helper.

BTW, to make your code works, we can add {this.props.children} in the App, like

render() { return ( <div> <h1>App</h1> <ul> <li><Link to="/about">About</Link></li> </ul> {this.props.children} </div> ) } 

Given your error of:

'Uncaught Error: Invariant Violation: Element type is invalid: expected a string (for built-in components) or a class/function but got: object'

You have 2 options:

1. Your export file can have the word default as in

export default class someNameHere 

Then your import will need to avoid using {} around it. As in

import somethingHere from someWhereHere 

2. Avoid using the default word. Then your export looks like

export class someNameHere 

Then your import must use the {}. Like

import {somethingHere} from someWhereHere 

In my case, that was caused by wrong comment symbols. This is wrong:

<Tag> /*{ oldComponent }*/ { newComponent } </Tag> 

This is correct:

<Tag> {/*{ oldComponent }*/} { newComponent } </Tag> 

Notice the curly brackets

I have the same error : ERROR FIX !!!!

I use 'react-router-redux' v4 but she's bad.. After npm install react-router-redux@next I'm on "react-router-redux": "^5.0.0-alpha.9",

AND IT'S WORK

I was having the same issue and realized that I was providing an Undefined React component in the JSX markup. The thing is that the react component to render was dynamically calculated and it ended up being undefined!

The error stated:

Invariant Violation: 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. Check the render method of C.,

The example producing this error:

var componentA = require('./components/A'); var componentB = require('./components/B'); const templates = { a_type: componentA, b_type: componentB } class C extends React.Component { constructor(props) { super(props); } // ... render() { //Let´s say that depending on the uiType coming in a data field you end up rendering a component A or B (as part of C) const ComponentTemplate = templates[this.props.data.uiType]; return <ComponentTemplate></ComponentTemplate> } // ... }

The problem was that an invalid "uiType" was provided and therefore this was producing undefined as result:

templates['InvalidString']

I got this by doing import App from './app/'; expecting it to import ./app/index.js, but it instead imported ./app.json.

Just as a quick addition to this. I was having the same problem and while Webpack was compiling my tests and the application was running fine. When I was importing my component into the test file I was using the incorrect case on one of the imports and that was causing the same error.

import myComponent from '../../src/components/myComponent' 

Should have been

import myComponent from '../../src/components/MyComponent' 

Note that the import name myComponent depends on the name of the export inside the MyComponent file.

Had similar issue with React Native latest versions 0.50 and up.

For me it was a difference between:

import App from './app' 

and

import App from './app/index.js' 

(the latter fixed the issue). Took me hours to catch this weird, hard to notice nuance :(

Another possible solution, that worked for me:

Currently, react-router-redux is in beta and npm returns 4.x, but not 5.x. But the @types/react-router-redux returned 5.x. So there were undefined variables used.

Forcing NPM/Yarn to use 5.x solved it for me.

In my case, the import was happening implicitly due to a library.

I managed to fix it by changing

export class Foo

to

export default class Foo.

I ran into this error when I had a .jsx and .scss file in the same directory with the same root name.

So, for example, if you have Component.jsx and Component.scss in the same folder and you try to do this:

import Component from ./Component

Webpack apparently gets confused and, at least in my case, tries to import the scss file when I really want the .jsx file.

I was able to fix it by renaming the .scss file and avoiding the ambiguity. I could have also explicitly imported Component.jsx

In my case I was using the default export, but not exporting a function or React.Component, but just a JSX element, i.e.

Error:

export default (<div>Hello World!</div>) 

Works :

export default () => (<div>Hello World!</div>) 

I got this error in react routing, problem was that I was using

<Route path="/" component={<Home/>} exact />

but it was wrong route requires component as a class/function so I changed it to

<Route path="/" component={Home} exact />

and it worked. (Just avoid the braces around the component)

And in my case I was just missing a semicolon at the import-decleration in one of my sub modules.

Fixed it by changing this:

import Splash from './Splash' 

to this:

import Splash from './Splash'; 

In addition to import/export issues mentioned. I found using React.cloneElement() to add props to a child element and then rendering it gave me this same error.

I had to change:

render() { const ChildWithProps = React.cloneElement( this.props.children, { className: `${PREFIX}-anchor` } ); return ( <div> <ChildWithProps /> ... </div> ); } 

to:

render() { ... return ( <div> <ChildWithProps.type {...ChildWithProps.props} /> </div> ); } 

See the React.cloneElement() docs for more info.

I was getting this error also. The error was being caused by trying to export a component like this...

export default Component(); 

Instead of like this...

export default Component; 

My understanding is that by adding the "()" at the end of the component, I was actually calling the function instead of just referencing it.

I did not see this in the answers above, but may have missed it. I hope it helps someone and saves some time. It took me a long time to pinpoint the source of this error!

The problem can also be an alias used for a default export.

Change

import { Button as ButtonTest } from "../theme/components/Button"; 

to

import { default as ButtonTest } from "../theme/components/Button"; 

solved the issue for me.

I was the same problem because I did import incorrect library, so i checked the documentation from the library and the route was changed with the new versión, the solution was this:

import {Ionicons} from '@expo/vector-icons'; 

and I was writing the incorrect way:

import {Ionicons} from 'expo'; 

Just want to add a case to this question. I walked around this issue by swapping the order of import, for example in my mixed of imports before:

import { Label } from 'components/forms/label'; import Loader from 'components/loader/loader'; ... import Select from 'components/select/select'; // <----- the error happen 

After the change:

import Select from 'components/select/select'; // <----- Fixed import { Label } from 'components/forms/label'; import Loader from 'components/loader/loader'; ... 

For me it was that my styled-components were defined after my functional component definition. It was only happening in staging and not locally for me. Once I moved my styled-components above my component definition the error went away.

It means some of your imported Components are wrongly declared or nonexistent

I had a similar issue, I did

import { Image } from './Shared' 

but When I looked into the Shared file I didn't have an 'Image' component rather an 'ItemImage' Component

import { ItemImage } from './Shared'; 

This happens when you copy code from other projects ;)

I had an issue with React.Fragment, because the version of my react was < 16.2, so I got rid of it.

I was getting this issue too. My imports look fine, I could copy the contents of my copy and paste it where it was being used and that worked. But it was the reference to the component that was going wrong.

For me I just had to shut down expo and restart it.

The error was fixed when I changed this code

AppRegistry.registerComponent(appName, App ); 

to this code :

AppRegistry.registerComponent(appName, () => App); 

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