Suspenders

Suspenders is a small TypeScript-first assertion and type-guard toolkit for runtime validation and type narrowing.

Installation

npm i @aliaksandarpratashchyk/suspenders

Usage

import { assert, isNumber, safe, unsafe } from "@aliaksandarpratashchyk/suspenders";

const value: unknown = "123";

// Type guard: narrow in an if-statement
if (isNumber(value)) {
  value.toFixed(2);
}

// Assertion: throws and narrows the type (via `asserts`)
assert(typeof value === "string");
assert.string(value);

// Safe cast: returns a typed value or throws a TypeError
const asNumber = safe.number;
const n = asNumber(123);

// Unsafe cast: no runtime checks
const definitelyNumber = unsafe<number>(value);

API Reference

• Run npm run build to regenerate API docs into docs/.

Scripts

• npm test — run the Jest suite, regenerate COVERAGE.md, and update coverage.svg.
• npm run build — bundle the library and regenerate API docs (docs/).
• npm run lint / npm run format — lint and format the codebase.

Publishing

GitHub Actions runs tests on pushes/PRs and publishes to npm when the version in package.json changes on main. Set NPM_TOKEN in repository secrets to enable publishing.