Now let's set up the actual TypeScript configuration and write the first, runnable file of our library management project.

Creating tsconfig.json

tsconfig.json controls HOW TypeScript checks and compiles our code – the central configuration file of every TypeScript project. Instead of writing it by hand, let's have it generated:

npx tsc --init

This produces a tsconfig.json with MANY commented-out options as documentation. We'll replace it with a lean, deliberately chosen configuration:

{
  "compilerOptions": {
    "target": "ES2022",
    "module": "NodeNext",
    "moduleResolution": "NodeNext",
    "outDir": "dist",
    "rootDir": "src",
    "strict": true,
    "esModuleInterop": true,
    "skipLibCheck": true,
    "forceConsistentCasingInFileNames": true
  },
  "include": ["src/**/*"]
}

The key options in detail

• "target": "ES2022" – up to which JavaScript version TypeScript is allowed to "downlevel" the code when compiling. Newer Node.js versions support ES2022 natively, so there's no reason to fall back to older syntax.
• "module"/"moduleResolution": "NodeNext" – matches our "type": "module" from package.json (chapter 2), uses modern ES module resolution instead of the older CommonJS system.
• "outDir"/"rootDir" – determine WHERE compiled .js files end up (dist/) and WHERE TypeScript source files are read from (src/) – important for npm run build from chapter 2.
• "strict": true – enables ALL strict type checks at once (including strictNullChecks, noImplicitAny) – ALWAYS recommended for a NEW project, we'll build on this throughout the tutorial.
• "skipLibCheck": true – skips type-checking .d.ts files in node_modules – considerably faster compilation, without risking type errors in THIRD-PARTY libraries.

src/index.ts: the first file

console.log('Welcome to the library management system!');

npm start

npm start (or tsx src/index.ts directly) prints "Welcome to the library management system!" to the console – tsx transparently compiles the file in the background, with no .js file ever visibly appearing anywhere.

Provoking a deliberate error

To see strict: true in action, add this line as a test:

let bookCount: number = 42;
bookCount = 'forty-two'; // error!

Your editor underlines 'forty-two' in RED: "Type 'string' is not assignable to type 'number'." – EXACTLY the moment we discussed conceptually in chapter 1, now live in your own project. Remove the broken line again before moving on.

This project's target structure

bibliotheks-app/
├── package.json
├── tsconfig.json
└── src/
    └── index.ts