pseudo code for child an sibling element comparisons

AuntieSister.js

function walk(n, o, update, target) {
  tree = update(n, o, target)
  n = n.firstChildElement
  o = o.firstChildElement
  target = tree.firstChildElement
  while (n || o) {
    walk(n, o, update)
    n = n.nextElementSibling
    o = n.nextElementSibling
  }
}

function update (n, o) {
  // fast returns
  // morph
  // return element
}