base

> Strict base TypeScript configuration with modern defaults. No include/exclude patterns, so you control what gets compiled.

✨ Features

🔒 Strict Mode: strict plus extra safety flags
🚀 Modern Defaults: ES2022 target with NodeNext modules
🎯 Flexible: no file patterns imposed
🗺️ Source Maps: source and declaration maps enabled

📦 Installation

npm install --save-dev @jmlweb/tsconfig-base typescript

🚀 Quick Start

{
  "extends": "@jmlweb/tsconfig-base",
  "compilerOptions": {
    "outDir": "./dist",
    "rootDir": "./src"
  },
  "include": ["src/**/*"],
  "exclude": ["node_modules", "dist"]
}

💡 Examples

Library with declarations in a monorepo

{
  "extends": "@jmlweb/tsconfig-base",
  "compilerOptions": {
    "outDir": "./dist",
    "rootDir": "./src",
    "composite": true
  },
  "include": ["src/**/*"],
  "exclude": ["node_modules", "dist", "**/*.test.ts"]
}

Relaxing options

{
  "extends": "@jmlweb/tsconfig-base",
  "compilerOptions": {
    "target": "ES2020",
    "noUncheckedIndexedAccess": false
  },
  "include": ["src/**/*"]
}

📋 Configuration Details

Option	Value	Description
`strict`	`true`	All strict type checking options
`target`	`ES2022`	Modern JavaScript output
`module`	`NodeNext`	Node.js ESM/CJS module system
`moduleResolution`	`NodeNext`	Node.js module resolution
`esModuleInterop`	`true`	CommonJS/ESM interoperability
`skipLibCheck`	`true`	Skip type checking of declaration files
`forceConsistentCasingInFileNames`	`true`	Enforce consistent file name casing
`declaration`	`true`	Generate `.d.ts` files
`declarationMap`	`true`	Generate maps for `.d.ts` files
`sourceMap`	`true`	Generate source maps
`noUncheckedIndexedAccess`	`true`	Add `undefined` to index signature access
`noImplicitOverride`	`true`	Require the `override` keyword
`noPropertyAccessFromIndexSignature`	`true`	Require bracket notation for index signatures
`exactOptionalPropertyTypes`	`true`	Differentiate `undefined` from optional
`noFallthroughCasesInSwitch`	`true`	Report fallthrough cases in `switch`
`isolatedModules`	`true`	Ensure transpiler compatibility
`verbatimModuleSyntax`	`true`	Enforce explicit type imports/exports
`resolveJsonModule`	`true`	Allow importing JSON files

You must set include, exclude and (recommended) outDir/rootDir yourself.

Common issues

“Relative import paths need explicit file extensions”: NodeNext requires .js extensions in relative imports (import { foo } from './bar.js'), or switch to bundler resolution (see below).
module/moduleResolution mismatch: override both together.
T | undefined on obj[key]: caused by noUncheckedIndexedAccess; use ?. or an explicit check.

🎯 When to Use

✅ Strict TypeScript for Node.js libraries and services
✅ A foundation for framework-specific configs
✅ Projects that want full control over file patterns

Not for the browser or JSX: use @jmlweb/tsconfig-react. Not for Node.js without DOM types in a bundler-free setup: use @jmlweb/tsconfig-node.

🔧 Extending the Configuration

Bundler-based resolution (ESM):

{
  "extends": "@jmlweb/tsconfig-base",
  "compilerOptions": {
    "module": "ESNext",
    "moduleResolution": "bundler"
  }
}

CommonJS:

{
  "extends": "@jmlweb/tsconfig-base",
  "compilerOptions": {
    "module": "CommonJS",
    "moduleResolution": "node"
  }
}

📝 Usage with Scripts

{
  "scripts": {
    "build": "tsc",
    "typecheck": "tsc --noEmit"
  }
}

npm run typecheck

📋 Requirements

Node.js >= 22.12.0
TypeScript >= 5.0.0

📦 Peer Dependencies

None declared. Install typescript (>= 5.0.0) in your project.

@jmlweb/tsconfig-node - extends this config for Node.js and CLIs
@jmlweb/tsconfig-react - extends this config for React
@jmlweb/tsconfig-astro - extends this config for Astro
@jmlweb/oxlint-config-base - Oxlint configuration for TypeScript projects (recommended)
@jmlweb/oxfmt-config-base - Oxfmt configuration (recommended)

🔄 Migration Guide

1.x → 2.0.0

Breaking: Node.js >=22.12.0 is now required (Node.js 18 and 20 are end-of-life).

Upgrade Node.js to 22.12.0 or later.
Update the package: npm install --save-dev @jmlweb/tsconfig-base@^2.0.0.

The compilerOptions are unchanged. See the Changelog.

📄 License

MIT