React: How to set propTypes stateless component.

react-proptypes.js

import React from 'react';

export class BestSeller extends React.Component {
  render() {
    return (
      <li>
        Title: <span>
          {this.props.title}
        </span><br />
        
        Author: <span>
          {this.props.author}
        </span><br />
        
        Weeks: <span>
          {this.props.weeksOnList}
        </span>
      </li>
    );
  }
}

// 1. Define propTypes as static object literal
// 2. The name of each property in propTypes should be the name of an expected prop

BestSeller.propTypes = {
  title: React.PropTypes.string.isRequired,
  author: React.PropTypes.string.isRequired,
  weeksOnList: React.PropTypes.number.isRequired
}