Don't name your variables after types:you wouldn’t name your pets “dog” or “cat”

That's good style. The important thing you will get out of the map is at the front of the variable name, and there's a less important little qualifier "byId" to help you understand how the data is structured.

Firstly, I have known several people to name their animals some variation of their type, but barring that.

I see it as a courtesy to myself than those that come after me to provide relevant context to a variable name. If the type in the scope of the variable is meaningful to its use then I will include it.

Good or bad code tells me what it does, rarely does it tell me what its supposed to do.