React for the UI,
Bootstrap for the CSS,
Backbone for REST and routing,
and a few other helper libraries I don't remember.
The server is Jetty with Jersey, using Akka for communication with a HSQLDB for data.
Back when IE 6 was still around I just used jQuery for everything, then we moved onto more full-blown frameworks like Ember, KnockoutJS, Backbone etc. Today at my work place we are using React which is working out ok, but I still maintain that after 10 years straight of fighting with JS, CSS and HTML, the best way is to just write it all from scratch yourself.
I could include thousands of lines in CSS and JS on my pages by using frameworks and libraries like React and Bootstrap, or I could write exactly what I need with 200 lines of CSS and a few dozen lines of JS.
Browsers are much more consistent with each other now, so gone are the days when things like jQuery were needed to iron out browser differences; the differences still exist of course, but it rarely causes a problem now.
The new fetch API for JS takes care of all my REST API requests using promises, and I write the REST API itself with Node, although I'm looking at changing over to Go.