Your JavaScript code doesn't involve a request at all, other than the one to initially load the page which is going to be a standard stateless HTTP request. The only stateful protocol you would possibly end up using in JavaScript code is a WebSocket. The rest of the web revolves around stateless HTTP requests.
That blog post has less to do with HTTP and more to do with applications. HTTP is stateless, but most web applications are not as they rely upon session data to track who is logged in or other details. That session data makes the application as a whole stateful even if the individual HTTP requests are not.