counter example with react

Example 1: simple counter react

import React, { useState } from 'react';
import ReactDOM from 'react-dom';

export const Counter = (props) => {
  const [count, setCount ] = useState(0)

  return (
    <div id="mainArea">
      button count: <span>{count}</span>
      <button id="mainButton" onClick={() => {setCount(count + 1)}}>Increase</button>
    </div>
  );

}

ReactDOM.render(
  <Counter />,
  document.getElementById('root')
);

Example 2: simple counter react

import React from 'react';
import ReactDOM from 'react-dom';

class Counter extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      count : 0
    }
    this.increment = this.increment.bind(this);
  }

  increment() {
    this.setState({count:this.state.count+1});
  }

  render() {
    return (
      <div id="mainArea">
        button count: <span>{this.state.count}</span>
        <button onClick={this.increment} id="mainButton">Increase</button>
      </div>
    );
  }
}

ReactDOM.render(
  <Counter />,
  document.getElementById('root')
);