code: function getIdxOfMatchingSelector(tNode, selector) {
      var localNames = tNode.localNames;
      if (localNames) {
          for (var i = 0; i < localNames.length; i += 2) {
              if (localNames[i] === selector) {
                  return localNames[i + 1];
              }
          }
      }
      return null;
  }
docs: Iterates over local names for a given node and returns directive index
  (or -1 if a local name points to an element).
  
  @param tNode static data of a node to check
  @param selector selector to match
  @returns directive index, -1 or null if a selector didn't match any of the local names