This counter uses React's functional components and the method useState(). However, useState() doesn't return a variable like you might think. Instead, it returns an array with a variable (in this case count) and a method to update that variable. The two buttons you see call that method.

It is important to note that this is all handled within the javascript for this webpage. If you refresh the page, the current state will be lost and the counter will reset. In the future, we can use Next.js' data fetching to keep track of count over longer periods of time.

You can look at the code for this page here.