Sorry if I wasn't clear enough. Yes I want something like an object in javascript, like a struct in C but at runtime. But I want to implement this myself. At first I thought a hash table was the right choice. But I don't need the insert delete increase capacity that this data structure typically needs to implement. I want to implement this in Mathematica. The language doesn't have native objects given that the main idea is for things to be immutable. But I still can program data structures, so I'm looking for one...