ES-modulsyntax: import och export

// math.ts
export function add(a: number, b: number): number { return a + b; }
export const PI = 3.14159;
export interface Config { host: string; }

// app.ts
import { add, PI } from './math';
console.log(add(1, 2)); // 3
console.log(PI);        // 3.14159

// greeter.ts
export default function greet(name: string): string {
  return 'Hello, ' + name;
}

// app.ts
import greet from './greeter';
console.log(greet('Alice'));

import { log as consoleLog } from './logger';
import { User as UserModel } from './models';

import * as math from './math';
console.log(math.add(1, 2));
console.log(math.PI);

// index.ts
export { add, PI } from './math';
export { greet } from './greeter';
export * from './utils';

// types.ts
export type { User, Product };
export type UserId = string;

import type { User } from './models';
// Only the type is imported — no JavaScript
function greet(user: User): string { return user.name; }

// tsconfig.json: "resolveJsonModule": true
import config from './config.json';
console.log(config.host); // typed based on JSON structure