Statelet — Typed Finite State Machines for TypeScript

Statelet is a tiny, fully-typed finite-state-machine library for TypeScript. Define states, events, guards and actions in one typed config and get a pure transition function plus a small createActor interpreter — with state names, event types and context all inferred and checked by the compiler. Zero runtime dependencies.

Highlights

• Real inference — invalid events and undeclared targets are compile errors.
• Pure transition(snapshot, event) — trivial to unit-test.
• createActor interpreter: start, send, getSnapshot, subscribe, can, stop.
• Guards block transitions; actions are pure context reducers (exit → transition → entry).
• Zero dependencies; builds with tsc to ESM + .d.ts.
• node:test suite + runnable examples that double as type tests.