[NTG-context] How to test the emptyness of a variable?

Any idea for achieving this behaviour? - When there is a chapter label (\setuplabeltext[chapter=CHAPTER~]), display : CHAPTER ONE Cool CHAPTER 2 Cat CHAPTER 3 Mouse etc. - When there is no chapter label (\setuplabeltext[chapter=]), display: 1 Cool 2 Cat 3 Mouse etc. My try achieves the first display, but not the second one since I don’t know how to test the emptyness of the chapter label. When I remove the chapter label, it displays: ONE Cool 2 Cat 3 Mouse instead of: 1 Cool 2 Cat 3 Mouse My code: \setuplabeltext[chapter=CHAPTER~] \define[1] \MyCommand{\doifelse{\currentsectioncountervalue}{1}{ONE}{#1}} \setuphead[chapter][deepnumbercommand=\MyCommand] \starttext \chapter{Cool} \chapter{Cat} \chapter{Mouse} \stoptext