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ReactJS isCompositeComponent() Method

  • Last Updated : 31 May, 2021

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 see how to use isCompositeComponent() method. The isCompositeComponent() method return true if instance is a user-defined component.

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.


import React from 'react';
import { isCompositeComponent } from 'react-dom/test-utils';
// Defining our App Component
const App = () => {
// Function to demonstrate isCompositeComponent() method
function func(){
   var a = isCompositeComponent(el);
   console.log("The Following is an element :", a);
const el = <div>
// Returning our JSX code
return <>
        <button onClick={func}>Click Here !!</button>
// 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:


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