I think UI programming almost always need a framework than a library, under these definitions of Library and Framework: Library = independent objects and methods that your code invokes; Framework = entry point to the app, controls the event loop that calls your code, and lets you hook into its lifecycle methods.

Under that definition, ReactJS is strictly a framework. But we tend to look at it as a library since unlike other monolithic frameworks (Angular, Rails etc.), it is quite small, composes well, and is not overly prescriptive.

While I don't think FOAM is the next-big-thing in Javascript frameworks (that award goes to React's component model), I am happy to see it focusing on the primacy of the data-structure and recognizing that good code flows from a good data structure. We can already use that philosophy in React by ensuring all components are annotated with propTypes, using a statically typed language (TypeScript), and clearly defining the API schema using something like JSON Schema (http://spacetelescope.github.io/understanding-json-schema/ab...).