What are type classes? A definition of a type class is a function that takes some type variables of a type and returns a new type that depends on thoose type variables. So it is like a function that operates on types.
This means that you have a free type variable that you can define some type constraint on a “class” of functions. This free type variable is called parametrically polymorphism. If this sound familiar to some Java and C# developers, this is also called generics.
In C# code:
In javscript code: