ReactJS isCompositeComponentWithType() Method

React.js library is all about splitting the app into several components. Each Component has its own lifecycle. React provides us some in-built methods that we can override at particular stages in the life-cycle of the component.

In this article, we will know how to use isCompositeComponentWithType() method. This method returns true if a component whose type is of a React componentClass.

Creating React Application And Installing Module:

• Step 1: Create a React application using the following command.

  
  
  

  npx create-react-app foldername

• Step 2: After creating your project folder i.e. foldername, move to it using the following command.

  cd foldername

Project Structure: It will look like the following.

Example: Now write down the following code in the App.js file. Here, App is our default component where we have written our code.

App.js

import React from 'react';
import { isCompositeComponentWithType } from 'react-dom/test-utils';

// Defining our App Component
const App = () => {

  // Function to demonstrate isCompositeComponentWithType() method
  function func() {
    var a = isCompositeComponentWithType(el);
    console.log("The Following element is"+
                " isCompositeComponentWithType :", a);
  }

  const el = <div>
      <h1>element</h1>
  </div>

  // Returning our JSX code
  return <>
      <div id='el'>
          <h1>GeeksforGeeks</h1>
          <button onClick={func}>
           Click Here !!
          </button>
      </div>
  </>;
}

// Exporting your Default App Component
export default App

Step to Run Application: Run the application using the following command from the root directory of the project:

npm start

Output: Now open your browser and go to http://localhost:3000/, you will see the following output:

Reference: https://reactjs.org/docs/test-utils.html#iscompositecomponentwithtype