Recompose

counter (stateful).js

import React, { Component } from 'react';

export default class Counter extends Component {
  constructor(props) {
    super(props);
    this.state = { counter: 0 };
    this.handleCount = this.handleCount.bind(this);
  }
  handleCount(count) {
    this.setState({ counter: this.state.counter + count });
  }
  render() {
    const { counter } = this.state;
    return (
      <div>
        Count: {counter}
        <button onClick={() => this.handleCount(1)}>Increase</button>
        <button onClick={() => this.handleCount(-1)}>Decrease</button>
      </div>
    );
  }
}