React iframe head

iframe.js

function mergeElements(target, source) {
  var seen = {};
  if (target.tagName != source.tagName) {
    console.log("tagname change:", target.tagName, source.tagName, source)
    target.parentNode.replaceChild(source, target);
    return;
  }
  _.each(source.attributes, function(att) {
      seen[att.nodeName] = true;
      if (att.nodeName === 'data-reactid') {
        return;
      }
      if (target.getAttribute(att.nodeName) !== att.value) {
        target.setAttribute(att.nodeName, att.value);
      }
  });
  _.each(target.attributes, function(att) {
      if (!att) {
        console.log("target atributes yielded falsey", att, target)
      } else if (!seen[att.nodeName]) {
        target.removeAttribute(att.nodeName);
      }
  });
  if ((target.textContent || source.textContent) &&
      (target.textContent !== source.textContent)) {
    target.textContent = source.textContent;
  }
};

var doc = this.getDOMNode().contentDocument;
var headMarkup = React.renderToString(head);
if (headMarkup) {
  //this.refs.head = head;
  var div = doc.createElement('div');
  div.innerHTML = headMarkup;
  var newNodes = _.toArray(div.childNodes); //first child is "head"
  var oldNodes = _.toArray(doc.querySelectorAll('head [data-reactid]'));
  //console.log("head nodes:", newNodes, div, head);

  var oldElements = {};
  var updatedElements = {};
  _.each(oldNodes, function(node, index) {
    var reactID = node.getAttribute('data-reactid').split('$')[1];
    oldElements[reactID] = {
      node: node,
      index: index
    };
  });

  _.each(newNodes, function(node, index) {
    if (!node) {
      console.log("why null node?", node, index);
      return; //why?
    }
    var reactID = (node.getAttribute('data-reactid') || "").split('$')[1];
    if (!reactID) {
      console.log("why no reactid?", node, reactID, index)
      return;
    }
    var oldNode = oldElements[reactID];
    //childNode[4].parentNode.insertBefore(childNode[4], childNode[3]);
    if (oldNode) {
      mergeElements(oldNode.node, node);
      if (oldNode.index !== index) {
          if (oldNodes.length > index) {
            doc.head.insertBefore(oldNode.node, oldNodes[index]);
          } else {
            //console.log("this shouldn't happen", index, oldNodes.length)
          }
      }
    } else {
      if (oldNodes.length <= index) {
        doc.head.appendChild(node);
      } else {
        doc.head.insertBefore(node, oldNodes[index]);
      }
      console.log("appended:", node, doc.head)
    }
    updatedElements[reactID] = node;
  });

  _.each(oldElements, function(oldNode, reactID) {
    if (!updatedElements[reactID]) {
      doc.head.removeChild(oldNode.node);
      console.log("removed:", reactID);
    }
  });
}