render() {
   const func = (node) => {
    React.Children.forEach(node.children, (childNode) => {
      if (childNode && childNode.props && typeof childNode.props.children === "object") {
        func(childNode.props);
      }
      else if (typeof childNode.props.children === "string"){
        console.log(childNode.props);
      }
    })
  }

  func(this.props);

  return <span>{ this.props.children }</span>;
}

class Hello extends React.Component {

  constructor() {
    super();

    this.state = {
      children: [
        <div>test</div>,
        <div>test2</div>
      ]
    };

    setTimeout(() => {
        this.setState({
        children: [
          <div>new!</div>,
          <div>changed!</div>
        ]
      });
    }, 2000);

  }

  render() {
    return <p>{this.state.children}</p>;
  }

}

ReactDOM.render(
  <Hello />,
  document.getElementById('container')
);

render() {
   const func = (children) => {
    React.Children.map(children, (childNode) => {
      if (typeof childNode.props.children === "string")
        return React.cloneElement(childNode, childNode.props, "something");
      return React.cloneElement(childNode, childNode.props, func(childNode.props.children));
    })
  }

  return <span>{ func(this.props.children) }</span>;
}