class Car extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      brand: "Ford",
      model: "Mustang",
      color: "red",
      year: 1964
    };
  }
  render() {
    return (
      <div>
        <h1>My {this.state.brand}</h1>
        <p>
          It is a {this.state.color}
          {this.state.model}
          from {this.state.year}.
        </p>
      </div>
    );
  }
}

class Clock extends React.Component {
  constructor(props) {
    super(props);
    this.state = {date: new Date()};
  }

  render() {
    return (
      <div>
        <h1>Hello, world!</h1>
        <h2>It is {this.state.date.toLocaleTimeString()}.</h2>
      </div>
    );
  }
}

class Message extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      message: ‘’    
    };
  }

  componentDidMount() {
    /* ... */
  }

  render() {
    return <div>{this.state.message}</div>;
  }
}

import React from 'react';

class Message extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      message: '',
      list: [],    
    };
  }
  /* ... */
}

const Message = () => {
  const [message, setMessage] = useState( '' );

  return (
    <div>
      <input
         type="text"
         value={message}
         placeholder="Enter a message"
         onChange={e => setMessage(e.target.value)}
       />
      <p>
        <strong>{message}</strong>
      </p>
    </div>
  );
};