doc.nodeType: 1
doc.nodeName: null
doc.nodeValue: null
doc.childNodes: <foo>bar</foo>,<x>y</x>
doc.toString(): <foo>bar</foo><x>y</x>
doc.firstChild.nodeType: 1
doc.firstChild.nodeName: foo
doc.firstChild.nodeValue: null
doc.firstChild.toString(): <foo>bar</foo>
doc.firstChild.firstChild.nodeType: 3
doc.firstChild.firstChild.nodeName: null
doc.firstChild.firstChild.nodeValue: bar
doc.firstChild.firstChild.toString(): bar
doc.firstChild.nextSibling: <x>y</x>
doc.firstChild.nextSibling.nodeName: x
doc.firstChild.nextSibling.nodeValue: null
///
doc2.nodeType: 1
doc2.nodeName: null
doc2.childNodes: <a hello="world">xxx</a>,<B>yyy</B>
doc2.toString(): <a hello="world">xxx</a><B>yyy</B>
doc2.firstChild.nodeName: a
doc2.firstChild.toString(): <a hello="world">xxx</a>
doc2.firstChild.nextSibling: <B>yyy</B>
JSON.stringify(doc2.firstChild.attributes): {"hello":"world"}
doc2.firstChild.nextSibling.nodeName: B
///
doc3.firstChild.firstChild: hello
doc4.firstChild.firstChild: world
