title: How to get the ReactJS element inside componentDidMount()?
body: <p>I have 4 instances of a certain React-class. After <code>componentDidMount()</code> I want to store the y-position of each instance.</p>
  
  <p>How can I address the rendered element? I cannot use classname, because I have 4 elements of the same class with different positions.</p>
  
  <p>My ReactJS component:</p>
  
  <pre><code>const Col = React.createClass({
      componentDidMount: function() {
          //here address the actual rendered col-instance
      },
  
      render() {
          return (
              &lt;div className='col'&gt;
              &lt;/div&gt;
          );
      }
  });
  </code></pre>