numbers.jsx

var Numbers = React.createClass({
  numbers() {
    return [3,4,5];
  },

  render() {
    return <div >
      <h1>There are {this.numbers().length} numbers</h1>
      {this.numbers().map(function(i){
          return <p>There is {i}</p>
        })
      }
    </div>
  }
});

React.render(<Numbers></Numbers>, document.body);