https://developer.mozilla.org/en-US/docs/Web/API/Element/firstElementChild

The Element.firstElementChild read-only property returns an element's first child Element, or null if there are no child elements.

Element.firstElementChild includes only element nodes. xmldom only implements Node.firstChild, that return all the child nodes, including non-element nodes like text and comment nodes.