Slight impurity in `calcScore` function about ramdatutorial

[knowthen]

That's a good observation... In hindsight, I believe what you're suggesting is a better option.

I'll throw out another thought, for consideration.
If groupedByProp is truly a constant (I'm treating it as such, but JavaScript doesn't support it), then calcScore would be considered pure.

A simpler example:

const PI = 3.14;

const radius = c => c / 2 * PI; 

So is radius pure? It's depending on PI?
If we just replaced PI in radius with 3.14, then most people would quickly identify it as pure... but many people look at PI and think it's referencing something outside it's parameters, so it wouldn't seem to be pure.

My answer... in a language that truly supports constants there's no difference between using PI or 3.14 in radius, so it's pure...
However we're in JavaScript so it's not as clear...
Regardless, I think your observation is legit and a better option.

Best,
James