Comment by headcanon

It depends on what you're doing, and what you're comfortable working with. If you have page content that is largely rendered server-side, with bits of interactivity and some basic AJAX on the frontend, jQuery's your friend. If you want to build a single-page application that rests mostly or entirely on the frontend, thats what the newer frameworks and methodologies are designed to do, and you're better off going with one of them.