I'm currently working on three different toy apps/learning projects: a Meetup clone in Svelte.js, an online store in React (with Redux, GraphlQL, etc.), and a simple todo with ReasonReact.
It's interesting to see how different framework tackle state management, UI rendering and the complexity of front-end development.
So far, I've found Svelte the easiest to grasp.
React has the best documentation and the best ecosystem.
ReasonReact is functional (OCaml with React bindings under the hood) and typed. As a fan of functional programming paradigms, that's a win.