code: function getTargets(data, context) {
      var results, ignored, lastPiece = data[data.length - 1];
      if (lastPiece.id) {
        results = finders.byId(lastPiece.id);
        ignored = "id";
      } else if (lastPiece.classList && lastPiece.classList.length && finders.byClassName) {
        results = finders.byClassName(lastPiece.classList, context);
        ignored = "classList";
      } else {
        results = finders.byTagName(lastPiece.tag || "*", context);
        ignored = "tag";
      }
      if (!results.length) return results;
      return filter(results, data, ignored);
    }
docs: 获得第一次目标节点集