preact-sigma

Purpose

preact-sigma is a typed state-model builder for Preact and TypeScript. It keeps top-level public state reactive, derived reads local to the model, writes explicit through actions, and side effects owned by explicit setup.

Installation

npm install preact-sigma

Quick Example

import { SigmaType } from "preact-sigma";

const Counter = new SigmaType<{ count: number }>("Counter")
  .defaultState({
    count: 0,
  })
  .computed({
    doubled() {
      return this.count * 2;
    },
  })
  .actions({
    increment() {
      this.count += 1;
    },
  });

const counter = new Counter();

counter.increment();

console.log(counter.count); // 1
console.log(counter.doubled); // 2

Documentation Map

• Concepts, lifecycle, invariants, and API selection live in docs/context.md.
• Quick-start usage lives in examples/basic-counter.ts.
• An advanced end-to-end example lives in examples/command-palette.tsx.
• Focused examples for non-obvious APIs live in examples/async-commit.ts, examples/observe-and-restore.ts, examples/signal-access.ts, and examples/setup-act.ts.
• Exact exported signatures live in dist/index.d.mts after pnpm build.