Need access to popupContainer element.

I am using rc-slider and I need to set the z-index for the element created by getContainer.
I also propose putting this logic inside componentDidMount() and clean up in componentWillUnmount.

Alternatively you could set the styling for the element within the portal. Right now it's a bit tricky to work with.

getContainer = () => {
  const { props } = this;
  const popupContainer = document.createElement('div');
  // Make sure default popup container will never cause scrollbar appearing
  // https://github.com/react-component/trigger/issues/41
  popupContainer.style.position = 'absolute';
  popupContainer.style.top = '0';
  popupContainer.style.left = '0';
  popupContainer.style.width = '100%';
  const mountNode = props.getPopupContainer ?
    props.getPopupContainer(findDOMNode(this)) : props.getDocument().body;
  mountNode.appendChild(popupContainer);
  return popupContainer;
}

Start by locating the getContainer implementation in the trigger code and read how the popup container is created and removed. The issue is done when callers can access or style the created container, with its lifecycle behavior covered by the relevant existing tests.