递归遍历孩子，按底向上、左到右顺序

function listNode (node) {
  if (!(node instanceof Node)) {
    throw new TypeError("parameter 1 is not of type 'Node'")
  }
  return Array.from(node.childNodes || [])
    .reduce((cList, cNode) => cList.concat(listNode(cNode)), [])
    .concat([node])
}

补：按底向上、左到右顺序并不一定是层次最深的排前面。可以用层序遍历倒过来记录：

function listNode (rootNode) {
  if (!(rootNode instanceof Node)) {
    throw new TypeError("parameter 1 is not of type 'Node'")
  }
  var queue = [rootNode, null]
  var levelNodes = []
  var result = []

  while (queue.length > 1) {
    var node = queue.shift()
    if (node === null) {
      queue.push(null)
      result = levelNodes.concat(result)
      levelNodes = []
      continue
    }
    
    levelNodes.push(node)
    if (node.hasChildNodes()) {
      queue = queue.concat(Array.from(node.childNodes))
    }
  }
  
  if (levelNodes.length > 0) {
    result = levelNodes.concat(result)
  }
  
  return result
}