I'm using enum because of TypeScript though. If you're not using TS you can do: export const sizes = { MD: 'md', // etc } The benefit is that you'll have the size names or button types all in the same place. If you need to change from lg to large you only need to change it in one place.

The only reason I would disagree with this is, lets picture you're using <Button size="md"> is hundreds of places in your app. Now, you get a requirement to change it from md to medium. With the enum you only need to change it in the Button component itself, you don't need to go over every single scenario where you're using it and change to medium.