score:1130

Accepted answer

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.

score:0

@Balasubramani M saved me here. Wanted to add one more to help people. This is the problem when you're gluing too many things together and being cavalier with versions. I updated a version of material-ui and need to change

import Card, {CardContent, CardMedia, CardActions } from "@material-ui/core/Card"; 

to this:

import Card from '@material-ui/core/Card';
import CardActions from '@material-ui/core/CardActions';
import CardContent from '@material-ui/core/CardContent';
import CardMedia from '@material-ui/core/CardMedia';

score:0

I had the same issue and the issue was some js files were not included in the bundling of that specific page. Try including those file and problem might be fixed. I did this:

.Include("~/js/" + jsFolder + "/yourjsfile")

and it fixed up the issue for me.

This was while I was using React in Dot NEt MVC

score:0

I've discovered another reason for this error. It has to do with the CSS-in-JS returning a null value to the top-level JSX of the return function in a React component.

For example:

const Css = styled.div`
<whatever css>
`;
export function exampleFunction(args1) {
  ...
  return null;
}

export default class ExampleComponent extends Component {
...
render() {
const CssInJs = exampleFunction(args1);
  ...
  return (
    <CssInJs>
      <OtherCssInJs />
      ...
    </CssInJs>
  );
}

I would get this warning:

Warning: React.createElement: type is invalid -- expected a string (for built-in components) or a class/function (for composite components) but got: null.

Followed by this error:

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

I discovered it was because there was no CSS with the CSS-in-JS component that I was trying to render. I fixed it by making sure there was CSS being returned and not a null value.

For example:

const Css = styled.div`
<whatever css>
`;
export function exampleFunction(args1) {
  ...
  return Css;
}

export default class ExampleComponent extends Component {
...
render() {
const CssInJs = exampleFunction(args1);
  ...
  return (
    <CssInJs>
      <OtherCssInJs />
      ...
    </CssInJs>
  );
}

score:0

I'm getting almost the same error:

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

I was trying to import a pure functional component from another node library my team has developed. To fix it, I had to change to an absolute import (referencing the path to the component inside node_modules) from

import FooBarList from 'team-ui';

to

import FooBarList from 'team-ui/lib/components/foo-bar-list/FooBarList';

score:0

In my case it ended up being the outer component imported like this:

import React, { Component } from 'react';

and then declared like:

export default class MyOuterComponent extends Component {

where an inner component imported the React bare:

import React from 'react';

and dotted into it for declaration:

export default class MyInnerComponent extends ReactComponent {

score:0

In my case, it took me a bunch of time to search out and checked may ways but only fixed by this way: remove "{", "}" when importing a custom component:

import OrderDetail from './orderDetail';

My wrong way was:

import { OrderDetail } from './orderDetail';

Because in the orderDetail.js file, I exported OrderDetail as the default class:

class OrderDetail extends Component {
  render() {
    return (
      <View>
        <Text>Here is an sample of Order Detail view</Text>
      </View>
    );
  }
}

export default OrderDetail;

score:0

I got this error while upgrading all libs to latest version

in older version following are imports

import { TabViewAnimated, TabViewPagerPan } from 'react-native-tab-view';

but in new version they are replaced with following

import { TabView, PagerPan } from "react-native-tab-view";

So be check proper all your import are available by using control click

score:0

In my case, it was the meta tags.

I was using

const MetaTags = require('react-meta-tags');

I guess MetaTags is a default export, So changing to this solved it for me, took hours to figure out which one was causing it.

const { MetaTags } = require('react-meta-tags');

score:0

exporting at the bottom of the file might solve it.

const IndicatorCloak = (props) => { ... }
export default IndicatorCloak;

score:0

By mistake i tried to import Container and Content from react-native instead of native-base.

Error because of this line:

import { ActivityIndicator, RefreshControl,  StyleSheet, View, Keyboard, Container, Content } from 'react-native';

Below is the code fix:

import { ActivityIndicator, RefreshControl,  StyleSheet, View, Keyboard } from 'react-native';
import { Container, Content} from 'native-base';

score:0

In my case I had written const Tab = createBottomTabNavigator instead of const Tab = createBottomTabNavigator()

score:0

Are you tired of naive import/export answers while you're nesting components?

Well, I've been, too, when trying to pass in props from parent to child, and the child was supposed to render sibling component.

Let say, you have a BaseDialog (parent) component, in which you want to have another component SettingsDialog (child) in which you want to render its independent component.

BaseDialog.tsx

import BaseButton from "./../BaseButton";
...
<SettingsDialog
  BaseButton={<BaseButton title="Connect Wallet" />}
/>

and you're trying to render in somewhere in Settings.Dialog.tsx the

const SettingsDialog = (props: {
  BaseButton: any;
}) => {
  const { BaseButton } = props;

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

(yes, it's a handy way to pass components parent->child, especially when they grow, but here it breaks), but it'll cause the Uncaught Error: Invariant Violation: Element type is invalid: expected a string (for built-in components) or a class/function but got: object error.

What you can do, to fix it, and still use the BaseButton, is to simply import it separately.

Settings.Dialog.tsx

import BaseButton from "./../BaseButton";

const SettingsDialog = () => {
  return(
    <div>
      <BaseButton title="Connect Wallet" />
    </div>
  );
}

and in parent simply

BaseDialog.tsx

<SettingsDialog />

What you're trying to achieve will be the same, and will fix this unintuitive, in this scenario, error.

In my examples, I've assumed that BaseDialog has a required prop with a name title.

score:0

Error? its definitely an import or export issue , you are reffering to a component or container that either you haven't exported from its defining script or when importing it u have used the wrong format.

Solution?

  1. Go through all your component/container definitions and make sure you have exported them at the end of the script i.e "export default 'yourcomponentname';" or at the beginning of the component definition i.e export const 'yourcomponentname'=() =>{ ....... }
  2. At your import statements make sure you have not mixed up named and default imports based on your corresponding export statements

score:0

In my case,

//details.js 
import React from 'react'

const Details = (props) =>{
return <h1>Details</h1>
}

export default Details;


//main.js
import React from "react";
import { withRouter } from "react-router";
import {Route,BrowserRouter as Router,Redirect,Switch,Link} from "react-router-dom";
import Details from "./myAccount/details";

const Main = (props) => {
 return (
   <>
        <Switch>
          <Route path="/my-account/details" component={<Details />} />
        </Switch>
   </>

 );
};

export default withRouter(Main);

===========================

Replaced with below one, error got fixed
component={<Details />}  with  component={Details} 

score:0

For me it was the name of app config json. In the index.js the imports were like this:

import { AppRegistry } from 'react-native'
import App from './app'
import { name as appName } from './app.json'

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

React Native does not differentiate between './app' and './app.json'. No idea why. So I've changed the name of the app.json to app.config.json and this has solved the problem:

import { AppRegistry } from 'react-native'
import App from './app'
import { name as appName } from './app.config.json'

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

score:1

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.

score:1

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 ;)

score:1

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

score:1

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.

score:1

The error was fixed when I changed this code

AppRegistry.registerComponent(appName, App );

to this code :

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

score:1

Under similar case, I had the same nasty error and I concentrated on the code but nothing above seemed to improve the situation. I was transferring from Javascript to Typescript but encountered that for some weird reason I had BOTH files at the same time. Removing the JS version solved it, that may save somebody's time.

score:2

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.

score:2

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';

score:2

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';
...

score:3

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.

score:3

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!

score:4

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';

score:5

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.

score:5

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

score:5

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>)

score:5

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)

score:6

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.

score:7

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 :(

score:8

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.

score:9

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

score:10

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']

score:12

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

score:13

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

score:19

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
  1. Avoid using the default word. Then your export looks like
export class someNameHere

Then your import must use the {}. Like

import {somethingHere} from someWhereHere

score:21

https://github.com/rackt/react-router/blob/e7c6f3d848e55dda11595447928e843d39bed0eb/examples/query-params/app.js#L4 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>

  )
}

score:23

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. https://github.com/reactjs/react-router-redux 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.

score:25

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.

score:27

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

score:55

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() { ...

score:187

you need export default or require(path).default

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

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