The Future of ReactJS
In practice, few real-world applications use just ReactJS. Additional technologies, such as Babel, ESLint, Redux, Flow/TypeScript, and Immutable.js, are typically brought in to help increase the maintainability of a codebase. Reason replaces the need for these additional technologies with its core language features.
ReasonReact is a Reason library that binds to ReactJS and provides a simpler, safer way to build ReactJS components. Just like ReactJS is just JavaScript, ReasonReact is just Reason. Additionally, it's easy to incrementally adopt because it was made by the same person who created ReactJS.
ReasonReact comes with a built in router, Redux-like data management, and JSX. You'll feel quite at home coming from a ReactJS background.
It's important to mention that Reason/ReasonReact is already being used by several companies in production, including within one of the largest codebases in the world. Facebook's messenger.com codebase is already over 50% converted to ReasonReact.
As a result, new releases of Reason and ReasonReact come with code mods that automate much, if not all, of the upgrade process for your code base. New features are thoroughly tested internally at Facebook before they're released to the public, and this results in a pleasant developer experience.