TypeScript template

A template for TypeScript projects: strict TypeScript, ESLint and Prettier, unit and mutation testing, and CI out of the box. Vite supplies bundling, CSS support, and a dev server with HMR, but it is a thin, interchangeable layer - the TypeScript tooling is the substance of the template.

See CONTRIBUTING.md for contributor conventions.

Requirements

• Node.js >= 24.15.0 (current LTS)

Usage

Run npm install at the root to install dependencies and link the packages declared in package.json.

Command	Description
npm start	Dev server with hot reload (localhost:5173 by default)
npm run build	Minified production build to dist/
npm run preview	Serve the built site (localhost:4173 by default)
npm run typecheck	Type-check application, packages and tooling without emitting
npm run lint	Lint with ESLint (warnings fail)
npm run lint-fix	Apply ESLint's automatic fixes
npm run format	Format the repo with Prettier
npm run format-check	Check formatting without writing
npm test	Run unit tests once
npm run test-changed	Run tests affected by changes since origin/HEAD, including uncommitted work
npm run mutation	Incremental mutation testing with Stryker
npm run verify-gate	Run the CI gate locally, without mutation testing
npm run test-watch	Run unit tests in watch mode

Notes

• index.html is the entry page. Vite uses its defaults without a configuration file, including its browser target and no production source maps.
• Vite transpiles TypeScript without type-checking. Run npm run typecheck to check types. npm run verify-gate includes it before the build and tests.
• test-changed is feedback while working, not a gate. Fetch a current origin/HEAD first. An unavailable comparison fails. Selection can miss deleted or renamed files, files read from disk and differences between staged and working content. The gate runs all tests. npm run verify-gate -- --shard=1/4 runs its other stages in full and only narrows the final test stage.
• TypeScript is pinned to the 6.x line.
• Mutation testing uses Stryker's incremental mode. Changes outside mutated source and test files can leave reused results stale; run npm run mutation -- --force for a fresh full run. CI does this on pushes to the default branch.