Similar to Jos's reply, vanilla JS is my choice. JS Frameworks have been proving themselves to be unstable, over the years, in my experience. AngularJS was proof of that, with the lack of those devs adopting Angular. React, amongst others, also box you in - and if you care about setting yourself apart from others in skill, the end result of your work will look much like theirs. Express is my only choice, if I need something up and ready to prototype, because it's minimal and I feel it's much more flexible.
Vue.js is something I've been studying over the past year, and I really feel that it's more of a library than a framework. Basically, jQuery with a better, more modern, approach - that encourages you to write and learn current vanilla techniques such as ES6, without just throwing something at the wall, and hoping it will stick, like most folks do with jQuery.