To implement component lifecycle methods in a Class Component:
Example:
import React, { Component } from 'react';
class LifecycleDemo extends Component {
  componentDidMount() {
    console.log('Component mounted');
  }
  componentDidUpdate() {
    console.log('Component updated');
  }
  componentWillUnmount() {
    console.log('Component will unmount');
  }
  render() {
    return <h1>Lifecycle Methods Demo</h1>;
  }
}
export default LifecycleDemo;