I use `ReactDOM.unstable_renderSubtreeIntoContainer` to render a portal.

``` javascript
class Modal extends React.Component {

componentDidMount() {
    this.node = document.createElement('div');
    document.body.appendChild(this.node);
    this.renderPortal(this.props);
}

componentWillReceiveProps(nextProps) {
    this.renderPortal(nextProps);
}

componentWillUnmount() {
    ReactDOM.unmountComponentAtNode(this.node);
    document.body.removeChild(this.node);
}

renderPortal = (props) => {
    renderSubtreeIntoContainer(this, <ModalPortal {...props} />, this.node);
}

render() {
    return null;
  }
}
```

In my root component:

``` javascript
class App extends React.Component {
    static childContextTypes = {
        highlightColor: React.PropTypes.object
    }

    getChildContext() {
        return {
            highlightColor: this.props.highlightColor
        }
    }

    ...
}
```

The context of root component will be updated and passed to children if  `this.props.highlightColor` is changed. This is right.
I can access the correct context in the `<ModalPortal/>` component in the first render.
And after that the context passed to  `<ModalPortal/>` **does not change any more** when the context of root component changed.
But I can access the correct context in the `<Modal/>`  every render.

what's wrong with my code ?

}
    var shouldReuseMarkup =
      containerHasReactMarkup &&
      !prevComponent &&
      !containerHasNonRootReactChild;
    var component = ReactMount._renderNewRootComponent(
      nextWrappedElement,
      container,
      shouldReuseMarkup,
      parentComponent != null ?
        parentComponent._reactInternalInstance._processChildContext(
          parentComponent._reactInternalInstance._context
        ) :
        emptyObject
    )._renderedComponent.getPublicInstance();
    if (callback) {
      callback.call(component);
    }
    return component;
  },
  /**
   * Renders a React component into the DOM in the supplied `container`.
   * See https://facebook.github.io/react/docs/top-level-api.html#reactdom.render
   *
   * If the React component was previously rendered into `container`, this will
   * perform an update on it and only mutate the DOM as necessary to reflect the
   * latest React component.
   *
   * @param {ReactElement} nextElement Component element to render.
   * @param {DOMElement} container DOM element to render into.