this.props.children undefined

You can’t access the children of your component through this.props.children. this.props.children designates the children being passed onto you by the owner:

  1. var App = React.createClass({
  2.   componentDidMount: function() {
  3.     // This doesn't refer to the `span`s! It refers to the children between
  4.     // last line's `<App></App>`, which are undefined.
  5.     console.log(this.props.children);
  6.   },
  8.   render: function() {
  9.     return <div><span/><span/></div>;
  10.   }
  11. });
  13. ReactDOM.render(<App></App>, mountNode);

To access your own subcomponents (the spans), place refs on them.