`'a' instanceof String => false` and `true instanceof Boolean => false`, the capitalized versions of JavaScript primitive types are avoided because they lead us to think that we're dealing with actual instances of those classes, when we're most often not (as in our case).

In TypeScript, we avoid the usage of `Object`, favoring `object` instead. Also, we use `void` as the return type of functions that return `undefined`, this indicates that we don't really care that it outputs `undefined`, it is `void`, which means that it's nothing and the return of it should be ignored.

By casting `'overflowX'|'overflowY'` to the `overflowProperty`, we tell the compiler (or type checker) which property we'll be accesing from the `CSSStyleDeclaration`. That's useful for IDEs such as VSCode, that uses the TypeScript parser to analyze the code. It can also be useful if we decide to add a type checker to the codebase later on.