docs: function domTraverseElements(node, opt_pre, opt_post) {
    var ret;
    if (opt_pre) {
      ret = opt_pre.call(null, node);
      if (typeof ret == 'boolean' && !ret) {
        return false;
      }
    }
  
    for (var c = node.firstChild; c; c = c.nextSibling) {
      if (c.nodeType == DOM_ELEMENT_NODE) {
        ret = arguments.callee.call(this, c, opt_pre, opt_post);
        if (typeof ret == 'boolean' && !ret) {
          return false;
        }
      }
    }
  
    if (opt_post) {
      ret = opt_post.call(null, node);
      if (typeof ret == 'boolean' && !ret) {
        return false;
      }
    }
  }