title: How to generate unique IDs for form labels in React?
body: <p>I have form elements with <code>label</code>s and I want to have unique IDs to link <code>label</code>s to elements with <code>htmlFor</code> attribute. Something like this:</p>
  
  <pre><code>React.createClass({
      render() {
          const id = ???;
          return (
              &lt;label htmlFor={id}&gt;My label&lt;/label&gt;
              &lt;input id={id} type="text"/&gt;
          );
      }
  });
  </code></pre>
  
  <p>I used to generate IDs based on <code>this._rootNodeID</code> but it’s unavailable since React 0.13. What is the best and/or simplest way to do it now?</p>