Summary - Modules

Write a multi-file accounting package with modules.

Summary - Modules

Modules let you split and share code across files. Named exports give multiple items, default exports give a single default, re-exports create barrel files, and import type brings in type-only items. A module can hold both named and default exports, enabling flexible API design.

// hesap.ts
export interface Islem { a: number; b: number; }
export default function hesapla(i: Islem) {
  return i.a + i.b;
}

Exercise Calculator package

Export interface Islem with properties a: number and b: number. Export hesapla as a default function with signature (i: Islem): number returning i.a + i.b. Print the result of hesapla({ a: 5, b: 7 }) with console.log.

Show example solution

export interface Islem {
  a: number;
  b: number;
}

export default function hesapla(i: Islem): number {
  return i.a + i.b;
}

console.log(hesapla({ a: 5, b: 7 }));

Test yourself

Can a module have both named and default exports at the same time?
- Yes, both can coexist
- Only default export is allowed
- Only named export is allowed
- No, only one kind is used
Show answer

Yes, both can coexist — A module can have both named and default exports at the same time. Named exports are unlimited, the default export is single; together they offer a flexible API.

Default export

export ____ function hesapla(i: Islem): number {
  return i.a + i.b;
}

Show answer

export default function hesapla(i: Islem): number {
  return i.a + i.b;
}

Match module concepts

export function topla

Named export
export default function

Default export
export { } from

Re-export
import type { }

Type-only import

Next lesson: What is a namespace?

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