title: Uncaught ReferenceError: ReactDOM is not defined
body: <p>So i have Rails applications, i installed react-rails gem, set it up and try to run test application.</p>
  
  <p>Freshly installed, when i tryed to run hello world program, this error hapened: </p>
  
  <blockquote>
    <p>Uncaught ReferenceError: ReactDOM is not defined</p>
  </blockquote>
  
  <p>This is my react: </p>
  
  <pre><code>var HelloWorld = React.createClass({
    render: function() {
      return (
        &lt;p&gt;
          Hello, &lt;input type="text" placeholder="Your name here" /&gt;!
          It is {this.props.date.toTimeString()}
        &lt;/p&gt;
      );
    }
  });
  
  setInterval(function() {
    ReactDOM.render(
      &lt;HelloWorld date={new Date()} /&gt;,
      document.getElementById('example')
    );
  }, 500);
  </code></pre>
  
  <p>Its saved inside /app/assets/javascripts/components/test.js.jsx file.</p>
  
  <p>Rails 4.2.4 With Ruby 2.2.3</p>