Integration

Build the working library by combining all parts.

Summary - Library package

In this project you combined all parts of a library package: type definitions with interface, generic helper functions, exports with a barrel file, and declarations with .d.ts. You built a coherent, type-safe, and reusable package.

interface Book { name: string; }
function first<T>(arr: T[]): T | undefined {
  return arr[0];
}

Final assembly

In the final assembly, index.ts imports and re-exports all modules; generic helpers serve the application; .d.ts provides types to JS consumers. Each part carries its own responsibility and together they form a coherent API.

// index.ts
export { Book, first } from "./core";

Exercise Library integration

The Kitap interface should have ad: string and yazar: string properties. The generic function firstElement<T>(arr: T[]): T | undefined should return arr[0]. The kitaplar array should contain two Kitap objects. Get the first book with firstElement(kitaplar) and print its .ad property with console.log.

Show example solution

interface Kitap {
  ad: string;
  yazar: string;
}
function firstElement<T>(arr: T[]): T | undefined {
  return arr[0];
}
const kitaplar: Kitap[] = [
  { ad: "TypeScript", yazar: "Ahmet" },
  { ad: "React", yazar: "Mehmet" }
];
const ilk = firstElement(kitaplar);
console.log(ilk.ad);

Test yourself

What is the most important principle during integration?
- Each part has a single responsibility
- Skip type declarations
- Avoid generic functions
- Write all code in a single file
Show answer

Each part has a single responsibility — In integration, each part having a single responsibility is key; types, helpers, barrel, and declarations are kept separate.

Import keyword

// index.ts
____ { Kitap } from "./types";

Show answer

// index.ts
import { Kitap } from "./types";

Integration parts

interface

Type definition
generic helper

Type-safe helper
barrel

Aggregated export
.d.ts

Declaration file

Next lesson: Question model

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