code: function (res, callback) {
          var fn = function (err, data) {
              if (err) {
                  return handleError(err, res);
              }
              callback(data);
          };
          return fn;
      }
docs: Useful for guarding callbacks. For example, say we have:  db.circles.getAll(function (err, circles) { if (err) { handleError(err, res); } <deal with circles> });  We can use 'guard' to do this instead:  db.circles.getAll(guard(res, function (circles) { <deal with circles> }));