Why am I Getting the \'Invariant Violation: Element type is invalid\' Error in React?

Invalid Element Type in React: "Invariant Violation" Error Explained

Problem

React developers frequently encounter the 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 puzzling error stems from an issue with the element type passed to React components.

Code Example

Consider the following code snippets:

main.js:

import React from 'react';
import ReactDOM from 'react-dom';
import Router from 'react-router';
import App from './components/App';
import About from './components/About';

ReactDOM.render((
  <Router>
    <Route path="/" component={App}>
      <Route path="about" component={About} />
    </Route>
  </Router>
), document.body);

About.jsx:

import React from 'react';
import RaisedButton from 'material-ui/lib/raised-button';

export default class About extends React.Component {
  render() {
    return (
        <RaisedButton label="Default" />
    );
  }
};

Cause of the Error

In this instance, the error was caused by a discrepancy in the import statement for the Home component in main.js. Using import {MyComponent} from '../components/xyz.js' instead of import MyComponent from '../components/xyz.js' resulted in the error. This difference in import syntax can lead React to interpret the imported component incorrectly, resulting in the "Invalid Element Type" error.

Solution

To resolve the issue, ensure that the correct import syntax is used for the component. In Webpack environments, this means using:

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

This syntax imports the component as a default export, which is the expected behavior for React components.

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