how to create class components in react js?

To create a class component in ReactJS, you can follow these steps:

1. Create a new JavaScript file in your React app's src directory. You can name the file anything you want, but it's common to use the name of the component as the file name, with a .js extension.
2. Import the React and Component modules from the react package at the top of your file:

import React, { Component } from 'react';         

1. Define a new class that extends the Component class from the react package. This class should have a render method that returns a JSX element that describes the UI of your component:

class MyComponent extends Component {
  render() {
    return (
      <div>
        <h1>Hello, World!</h1>
      </div>
    );
  }
}         

1. Export your component class by default, so it can be imported and used in other parts of your app:

export default MyComponent;         

Here's an example of what your complete class component file might look like:

import React, { Component } from 'react';
class MyComponent extends Component {
  render() {
    return (
      <div>
        <h1>Hello, World!</h1>
      </div>
    );
  }
}
export default MyComponent;         

You can now use this component in your app by importing it and rendering it in another component or in your app's root component