The firstChild of Node for JS returns the first child.
node.firstChild
lastChild
baseURI
childNodes
cloneNode
compareDocumentPosition
contains
getRootNode
hasChildNodes
isConnected
isEqualNode
nextSibling
nodeName
nodeType
normalize
ownerDocument
parentElement
parentNode
previousSibling
Web Hypertext Application Technology Working Group (WHATWG)
