parent(node, selector) {
			if (this.elem(node) && node.closest)
				return node.closest(selector);

			while (this.elem(node))
				if (this.matches(node, selector))
					return node;
				else
					node = node.parentNode;

			return null;
		}
Returns the closest parent node that matches the given query
selector expression.

This function is a convenience wrapper around the standard
`Node.closest("selector")` function with the added benefit that
the `node` argument may be a non-`Node` value, in which case
this function simply returns `null`.

@instance
@memberof LuCI.dom
@param {*} node
The `Node` argument to find the closest parent for.

@param {string} [selector]
The query selector expression to test against each parent.

@returns {Node|null}
Returns the closest parent node matching the selector or
`null` when the node argument is no valid DOM `Node` or the
selector didn't match any parent.