jflow

Minimal flow/state-machine pipeline library for JavaScript and TypeScript.

Install

pnpm add jflow

Quickstart

import { createFlow, done, next, run } from "jflow";

type Data = { count: number };

const flow = createFlow<Data, undefined, "start" | "step" | "done">({
  initial: "start",
  states: {
    start: (data) => next("step", { count: data.count + 1 }),
    step: (data) => next("done", { count: data.count + 1 }),
    done: (data) => done(data)
  }
});

const result = await run(flow, { count: 0 });
console.log(result.count);

API

createFlow

createFlow({ initial, states })

• initial: starting state key
• states: map of state handlers

run

run(flow, input, options?)

• options.context: context passed to handlers
• options.maxSteps: guard for infinite loops (default 10000)
• options.onState: called before each handler
• options.onTransition: called after each transition
• options.onError: called when a handler throws or returns error

Transition helpers

next(state, data)
done(data)
error(err, data?)

Demo

Order processing example:

pnpm demo

The demo source is in demo/index.ts.

Appendix

This project is inspired by Clojure's flow project and adapts similar ideas to a minimal JS/TS API.