This article seems to be making up its own terminology and patterns. In JS, a getter is a function bound to a property that is called when that property is accessed. (mdn.io/getter) and a setter is a function bound to a property that is called when the property is set (mdn.io/setter). In JS there isn't any real differentiation you need to make between a function with 0 arguments, a function with 1 argument, and a function with N arguments. They're all functions with some arity that you can call.