[markplindsay]

React is my only choice for single-page apps, but it's unnecessary for ordinary JS UI widgets on a mostly server-rendered site.

For UI elements that have a lot of internal state, React can remove a ton of complexity. However, the delay between initial page render and the React component rendering itself can sometimes be distracting when those elements are key parts of the UI. This is a solved problem if you're using Node on the server, obviously, but if you're rendering pages with other server-side technology it is a drawback to React. jQuery does not have these issues as it just attaches itself to the server-rendered markup.