Jane Street's Bonsai: A UI Library That Treats State Like LEGO
Bonsai: Janestreet's UI Library
Jane Street's Bonsai is a UI library for building reactive web apps in OCaml, used internally for everything from corporate directories to trading tools. Unlike frameworks that fuse state, incrementality, and rendering into one component, Bonsai lets you compose these primitives a la carte. This separation enables efficient incremental updates and flexible state management, even for complex scenarios like tabbed interfaces. Built on OCaml, it allows sharing types and logic between backend and frontend, and comes with a powerful templating language and expressive testing tools.
The same primitives that prevent re-rendering the entire page during user interaction can also be used to incrementalize an expensive business logic computation on a live-updating dataset.