TypeScript Configuration

The template uses TypeScript 5.x with strict mode, extending the official @tsconfig/strictest preset for library-grade type safety.

Configuration File

{
  "$schema": "https://json.schemastore.org/tsconfig",
  "extends": "@tsconfig/strictest",
  "compilerOptions": {
    // Target environment
    "target": "ES2022",
    "lib": ["ES2022"],
    // "lib": ["ES2022", "DOM", "DOM.Iterable"],  // Uncomment for Browser
    // "jsx": "react-jsx",                         // Uncomment for React

    // Module system (works with tsdown bundler)
    "module": "ESNext",
    "moduleResolution": "bundler",

    // Emit (tsdown handles actual output)
    "noEmit": true,
    "declaration": true,
    "declarationMap": true,

    // Additional
    "resolveJsonModule": true
  },
  "include": ["src"],
  "exclude": ["node_modules", "dist"]
}

Inherited from @tsconfig/strictest

The base preset provides these strict settings automatically:

• strict - All strict type-checking options
• noUnusedLocals / noUnusedParameters - Catch unused code
• noFallthroughCasesInSwitch - Prevent switch fallthrough bugs
• noUncheckedIndexedAccess - Add undefined to indexed access results
• isolatedModules - Ensure files can be transpiled independently
• verbatimModuleSyntax - Enforce explicit type imports
• esModuleInterop / skipLibCheck - Compatibility settings

Target Switching

The default configuration targets Node.js 20+. To target other environments, modify the lib and add relevant options.

For Browser Libraries

Add DOM types to the lib array:

{
  "compilerOptions": {
    "lib": ["ES2022", "DOM", "DOM.Iterable"]
  }
}

For React Libraries

Add JSX support and DOM types:

{
  "compilerOptions": {
    "lib": ["ES2022", "DOM", "DOM.Iterable"],
    "jsx": "react-jsx"
  }
}

TIP

You may also want to add @types/react as a dev dependency and update ESLint globals to include browser alongside node.

Customization

Adding Path Aliases

{
  "compilerOptions": {
    "baseUrl": ".",
    "paths": {
      "@/*": ["src/*"]
    }
  }
}

WARNING

If you add path aliases, update tsdown.config.ts to handle them during build.

Relaxing Strict Mode (Not Recommended)

If migrating existing code:

{
  "compilerOptions": {
    "strict": false,
    "noImplicitAny": false
  }
}

Type Checking

Run type checking without emitting files:

bun run typecheck

This is also run automatically on pre-commit via Lefthook.