Fulcro

Fulcro is an open-source framework for building web applications in ClojureScript. It provides a client-side runtime for React-based UIs and a data-centric model that ties the user interface to a single, normalized application state. The framework emphasizes declarative data requirements, predictable state transitions, and efficient server communication.

Core concepts: the app maintains a normalized cache of entities, each with a unique ident. Components declare the data they need via queries, and the UI renders as a function of the current app data. Data loading and mutations drive server updates; responses merge into the cache and trigger re-renders. Optimistic updates and incremental loading are supported.

Architecture and data flow: components define idents and queries; on mount or interaction, the client issues loads or mutations to a remote server. Server responses are normalized and merged, enabling data sharing across components. Fulcro supports a pluggable remote layer and can communicate over EDN or Transit formats.

Tooling and ecosystem: Fulcro works with CLJS toolchains such as Leiningen or Shadow CLJS, and often uses Pathom to assist server-side query planning. It integrates with React for rendering and emphasizes a cohesive end-to-end framework.

Usage and scope: Fulcro is used to build interactive dashboards, forms, and collaboration tools where predictable state and scalable data fetching are important. It targets ClojureScript stacks and offers a data-driven alternative to more imperative UI libraries, with a trade-off of a steeper learning curve.