React PropTypes validators for DOM nodes.
- `domNode`: Ensure the prop has been supplied a DOM node, `undefined`, or `null`.
- `domNode.isRequired`: Ensure the prop has been supplied a DOM node or `null`.
- `domNodeOf(type: string)`: Ensure the prop has been supplied a DOM node with the specified HTML tag, `undefined`, or `null`.
- `domNodeOf(type: string).isRequired`: Ensure the prop has been supplied a DOM node with the specified HTML tag or `null`.
isRequired variants allow null to be provided in order to prevent warnings from being emitted during initial render when passing a ref.