Packaging Helpers with Types & Tests for a Dependable TypeScript Toolbox

Here is how I turn small JavaScript helpers into reusable packages with TypeScript types, focused unit tests, a clean export surface, and a lean build, so fixes land once and propagate everywhere.

by Andrew Magill

Published on

Small utility functions — helpers — become force multipliers when they can be reliably shared and maintained across projects. These tiny workhorses streamline development, improve maintainability, and make developer lives easier. This workflow packages helpers with TypeScript types, focused unit tests, a clean export surface, and a lean build, so fixes land once and propagate everywhere. The goal is a compact, repeatable toolbox that stays predictable as it grows.

Best Practices for Packaging Helpers

  • Single responsibility. Each helper does one thing and composes cleanly. This minimizes breakage risk and keeps surface area obvious when reusing across apps.
  • Predictable inputs/outputs. Validate inputs, normalize types (e.g., Date | string), and either return a sensible default or throw with a clear message. This helps prevent hidden consumer bugs.
  • Types and tests. Provide TypeScript declarations and a small test per helper. This catches misuse at compile time and protects against regressions when refactoring.
  • Concise docs. Keep README short: install, API, a few usage snippets, and brief upgrade notes for breaking changes. The target is low maintenance, not exhaustive documentation chores.

Practical use-cases for Helpers

Imagine you want to maintain a small set of functions across several frontends: a date formatting helper and a tiny analytics-event normalizer. Duplicating logic across repos introduces drift and bugs. Packaging those helpers lets you fix issues once and consume consistent behavior everywhere.

Export the helpers to provide a stable API surface. Example (index.js):

export { analyticsEvent } from './events/analyticsEvent';
export { formatUtc } from './date/formatUtc';

Publish your utilities as a package (for example @your-scope/utils) and consumers can install what they need without pulling the whole toolbox:

Install with npm

npm install @your-scope/utils

Then you may import your helpers with @your-scope, wherever needed:

// component/someComponent.js or lib/library.js
import { analyticsEvent } from '@your-scope/events/analyticsEvent';
import { formatUtc } from '@your-scope/date/formatUtc';

Toolbox layout

Favor domain-based folders over a flat “utils” dump. This scales without creating a grab-bag.

src/
date/
formatUtc.ts
events/
analyticsEvent.ts
string/
slugify.ts
index.ts

Package example

Here is how to structure the package.json to specify details about filenames, types, building and testing:

{
	"name": "@your-scope/helpers",
	"version": "0.1.0",
	"type": "module",
	"main": "dist/cjs/index.js",
	"module": "dist/esm/index.js",
	"files": ["dist", "README.md"],
	"types": "dist/index.d.ts",
	"scripts": {
		"build": "rollup -c",
		"test": "node ./test/run.js"
	}
}

TypeScript-first approach

Prefer authoring in TypeScript and emitting declarations automatically.

tsconfig.json (library-focused essentials):

{
	"compilerOptions": {
		"target": "ES2020",
		"module": "ESNext",
		"declaration": true,
		"declarationMap": true,
		"outDir": "dist/esm",
		"moduleResolution": "Bundler",
		"strict": true,
		"skipLibCheck": true,
		"emitDeclarationOnly": true,
		"stripInternal": true
	},
	"include": ["src"]
}

Closing

Packaging helpers can make small pieces of code more maintainable, reliable, and discoverable across projects. The next time you find repetitive code or a domain-specific need, pause and ask, "Is it better to split out this functionality into a reusable helper?" Knowing when to use your own utilities improves your workflow and code quality.

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