walkDom.js

function walkDom(rootNode, iterator){
  var currentNode = rootNode.firstChild
  while (currentNode){
    iterator(currentNode)
    if (currentNode.firstChild){
      currentNode = currentNode.firstChild
    } else {
      while (currentNode && !currentNode.nextSibling){
        if (currentNode !== rootNode) {
          currentNode = currentNode.parentNode
        } else {
          currentNode = null
        }
      }
      currentNode = currentNode && currentNode.nextSibling
    }
  }
}