TypeScript — Configuration

tsconfig.json

The TypeScript configuration file controls compiler behavior:

{
  "compilerOptions": {
    "target": "ES2020",
    "module": "ESNext",
    "strict": true,
    "outDir": "./dist",
    "rootDir": "./src"
  },
  "include": ["src/**/*"],
  "exclude": ["node_modules", "dist"]
}

Essential compiler options

target

What JavaScript version to compile to:

{
  "compilerOptions": {
    "target": "ES2020"  // ES5, ES6, ES2015-ES2024, ESNext
  }
}

module

Module system for output:

{
  "compilerOptions": {
    "module": "ESNext"  // CommonJS, AMD, UMD, ESNext, NodeNext
  }
}

strict

Enable all strict type-checking options:

{
  "compilerOptions": {
    "strict": true
  }
}

This enables:

• strictNullChecks
• strictFunctionTypes
• strictBindCallApply
• noImplicitAny
• noImplicitThis
• alwaysStrict

outDir and rootDir

{
  "compilerOptions": {
    "outDir": "./dist",
    "rootDir": "./src"
  }
}

Strict mode options

{
  "compilerOptions": {
    "strictNullChecks": true,        // null/undefined checks
    "strictFunctionTypes": true,      // Function parameter checks
    "strictBindCallApply": true,      // Bind/call/apply checks
    "noImplicitAny": true,           // Error on implicit any
    "noImplicitThis": true,          // Error on implicit this
    "alwaysStrict": true,            // Emit "use strict"
    "noImplicitReturns": true,       // Error on missing returns
    "noFallthroughCasesInSwitch": true // Error on switch fallthrough
  }
}

Path mapping

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

// Now you can use clean imports
import { formatDate } from "@utils/date";
import { User } from "@types/models";

Declaration files

{
  "compilerOptions": {
    "declaration": true,          // Generate .d.ts files
    "declarationMap": true,       // Generate declaration maps
    "sourceMap": true             // Generate source maps
  }
}

JSX support

{
  "compilerOptions": {
    "jsx": "react-jsx"  // react, react-jsx, preserve
  }
}

Include and exclude

{
  "include": ["src/**/*", "types/**/*"],
  "exclude": ["node_modules", "dist", "**/*.test.ts"]
}

References

For project references (monorepos):

{
  "references": [
    { "path": "./packages/shared" },
    { "path": "./packages/api" }
  ],
  "files": []
}

Practical configs

Node.js project

{
  "compilerOptions": {
    "target": "ES2020",
    "module": "NodeNext",
    "moduleResolution": "NodeNext",
    "outDir": "./dist",
    "rootDir": "./src",
    "strict": true,
    "esModuleInterop": true,
    "skipLibCheck": true,
    "forceConsistentCasingInFileNames": true,
    "resolveJsonModule": true,
    "declaration": true,
    "declarationMap": true,
    "sourceMap": true
  },
  "include": ["src/**/*"],
  "exclude": ["node_modules", "dist"]
}

React project

{
  "compilerOptions": {
    "target": "ES2020",
    "module": "ESNext",
    "moduleResolution": "bundler",
    "jsx": "react-jsx",
    "outDir": "./dist",
    "strict": true,
    "esModuleInterop": true,
    "skipLibCheck": true,
    "forceConsistentCasingInFileNames": true,
    "noEmit": true,
    "isolatedModules": true
  },
  "include": ["src/**/*"]
}

Best practices

• Always enable strict: true
• Use moduleResolution: "NodeNext" for modern projects
• Enable noUnusedLocals and noUnusedParameters for cleanliness
• Use skipLibCheck: true for faster compilation
• Use forceConsistentCasingInFileNames: true for cross-platform

Mini Practice

1. Create a tsconfig.json with strict mode enabled
2. Set up path aliases for your project
3. Configure for a Node.js project
4. Add declaration file generation

Up Next

Congratulations! You've completed the TypeScript fundamentals. Continue exploring advanced topics like decorators, template literal types, and conditional types.