text: import React, { PropTypes } from 'react';
  
  export default function Counter({ count, onIncrement, onDecrement }) {
    return (
      <div>
        <h2>{ count }</h2>
        <button onClick={onIncrement}>+</button>
        <button onClick={onDecrement}>-</button>
      </div>
    )
  }
  
  Counter.propTypes = {
    count: PropTypes.number.isRequired,
    onIncrement: PropTypes.func.isRequired,
    onDecrement: PropTypes.func.isRequired,
  }
  