Tutorial 22-II is it the script still valid?

[touxstone]

I got stuck here once introduced the following below changes to the public/scripts/example.js source file and modify for testing the comments.json file reloading localhost:3001 gives me just a blank page.. I cannot see where the mistake is.. got bind sudenly..

var CommentBox = React.createClass({
  loadCommentsFromServer: function() {
    $.ajax({
      url: this.props.url,
      dataType: 'json',
      cache: false,
      success: function(data) {
        this.setState({data: data});
      }.bind(this),
      error: function(xhr, status, err) {
        console.error(this.props.url, status, err.toString());
      }.bind(this)
    });
  },
  getInitialState: function() {
    return {data: []};
  },
  componentDidMount: function() {
    this.loadCommentsFromServer();
    setInterval(this.loadCommentsFromServer, this.props.pollInterval);
  },
  render: function() {
    return (
      <div className="commentBox">
        <h1>Comments</h1>
        <CommentList data={this.state.data} />
        <CommentForm />
      </div>
    );
  }
});

// substitution the previous ReactDOM done....
ReactDOM.render(
  <CommentBox url="/api/comments" pollInterval={2000} />,
  document.getElementById('content')
);