In general, you're unlikely to need them. Instead of cobbling together disparate libraries for a virtual dom (React), state (Redux), immutability (Immutable.js

In general, you're unlikely to need them. Instead of cobbling together disparate libraries for a virtual dom (React), state (Redux), immutability (Immutable.js), and types (Flow / TypeScript), the entire language and its core libraries are developed as a holistic (but still modular) unit. In this way, Elm is the BSD to JavaScript's GNU/Linux. Strong typing and immutability are baked directly into the core language, elm-lang/html includes an efficient Virtual DOM, and Redux-style action / reducer cycles tend to naturally arise from "The Elm Architecture," and don't need significant support beyond what's already in the core language. If you've bought into the React/Redux paradigm, it's worth giving Elm a shot: the entire language and core libraries are intentionally designed to more cleanly, reliably, and maintainably implement the same structure.