The basemapLayerIds property is not retrieved under map objects and is returned as undefined when a map is created using the arcgisUtils.createMap method.
Bug ID Number
August 27, 2015
December 1, 2020
Operating System Version
7.0 64 Bit
After review by the development team, it has been determined that this issue is related to a known limitation with the software that lies outside of Esri's control. The issue's Additional Information section may contain further explanation.
This is a known issue and will be addressed in the 4.x versions of the API.