class-component-with-state.js

import React, { Component } from 'react';

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

  setCount(count) {
    this.setState({ count });
  }

  render() {
    return (
      <div>
        <p>You clicked {this.state.count} times</p>
        <button onClick={() => this.setCount(this.state.count + 1)}>
          Click me
        </button>
      </div>
    )
  }
}