incrementer.js

import React, { Component } from 'react';

export default class App extends Component {
  render() {
    return (
      <div className='container'>
        <Counter increment={1} />
        <Counter increment={5} />
        <Counter increment={15} />
        <Counter increment={25} />
      </div>
    );
  }
}

class Counter extends Component {
  constructor(props) {
    super(props);
    this.state = {
      count: 0,
    };
  }
  render() {
    return (
      <div>
        <input
          value={this.state.count}
        />
        <button
          onClick={() => {
            this.setState({
              count: this.state.count + this.props.increment,
            });
          }}>Increment by {this.props.increment}!
        </button>
      </div>
    );
  }
}

Counter.propTypes = {
  increment: React.PropTypes.number.isRequired,
};