ES6 classes and ReactJS: implementing propTypes
I think you're just supposed to do this:

CallerDetailsPanel.propTypes = { callerData: React.PropTypes.object }


This feels a little backwards, but the React team has done this with the hope that in the future, with ES7, you will be able to use a syntax that looks something like this:

class CallerDetailsPanel {
  static propTypes = { callerData: React.PropTypes.object }
  render() {
    return (
      &lt;div className='caller-details-panel'&gt;
        &lt;CallerCard person={this.props.callerData.owner} /&gt;
        &lt;CallerCard person={this.props.callerData.user} /&gt;
      &lt;/div&gt;
    )
  }
}