Modules – ES6 Imports/Exports & Namespaces

ES6 Module Syntax

// utils.ts
export function sum(a: number, b: number): number {
  return a + b;
}
export const PI = 3.1415;

// main.ts
import { sum, PI } from "./utils";
console.log(sum(2, 3), PI);

Default Export

// logger.ts
export default function log(msg: string) { console.log(msg); }

// app.ts
import log from "./logger";
log("started");

Re‑exporting

export * from "./utils"; // barrel file

Namespaces (legacy)

namespace Geometry {
  export interface Circle { radius: number; }
  export function area(c: Circle) { return Math.PI * c.radius ** 2; }
}

const c: Geometry.Circle = { radius: 5 };
console.log(Geometry.area(c));