docs: function resolveValueOrNodeSkel(index, val, valDefault) {
      switch (typeof(val)) {
        case "string":
          return resolveNodeSkel(index, val);
        case "undefined":
          if (valDefault === undefined) {
            throw "Unable to get value'" + val + "'";
          }
          return () => valDefault;
        default:
          return () => val;
      }
    }