The application they build uses jQuery on the client side, Websockets, Node / Express.js, and MongoDB. The focus is on seeing something built end-to-end, so there are a bunch of footnotes where they recommend investigating other technologies (e.g. a templating engine like handlebars). The UI is built purely with jQuery event passing, which seems to be falling out of favor. if you are familiar with React, Angular, etc it can still helpful to see what areas those tools improve. The authors also show the CSS changes they make as they go, which is great as it is one of the more rage inducing parts of web development.