code: function hashOnRejected (node) {
          // A node shouldn't be checked twice.
          if (node._umark)
              return true;
          else
              node._umark = true;
  
          var i = 0
              , len = node._pCount
              , child;
  
          while (i < len) {
              child = node[i++];
              if (child._onRejected || hashOnRejected(child)) return true;
          }
      }
docs: iterate tree