...

static getDerivedStateFromProps(nextProps, prevState) {
  // Store prevId in state so we can compare when props change.
  // Clear out previously-loaded data (so we don't render stale stuff).
  if (nextProps.id !== prevState.prevId) {
    return {
      externalData: null,
      prevId: nextProps.id
    };
  }

  // No state update necessary
  return null;
}

...