this.props.children undefined

你没办法通过 this.props.children 取得当前组件的子元素。 因为this.props.children 返回的是组件拥有者传递给你的 passed onto you 子节点。

var App = React.createClass({
  componentDidMount: function() {
    // This doesn't refer to the `span`s! It refers to the children between
    // last line's `<App></App>`, which are undefined.
    console.log(this.props.children);
  },

  render: function() {
    return <div><span/><span/></div>;
  }
});

React.render(<App></App>, mountNode);

如果想看更多地例子， 可以参考在 front page 里最后一个例子。