Modules in TypeScript

// Exporting
export interface User { id: number; name: string; }
export const API_URL = "https://api.example.com";
export function formatDate(d: Date): string { return d.toISOString(); }

// Default export
export default class UserService { /* ... */ }

// Importing
import UserService, { User, API_URL, formatDate } from "./user-service";
import type { User } from "./types";      // Type-only import (erased at runtime)
import { type User, type Config } from "./types";

// Barrel file — re-export from multiple modules
export { User, UserService } from "./user-service";
export { ApiClient } from "./api-client";
export { Logger } from "./logger";

// Re-export with rename
export { User as AppUser } from "./user-service";

// Re-export everything
export * from "./types";
export * from "./utils";