Modules: import & export

Named exports

A file can export as many named values, functions, types or interfaces as it needs.

// math.ts
export function add(a: number, b: number): number {
  return a + b;
}
export interface Point {
  x: number;
  y: number;
}

Default export & import

A file has at most one export default — imported without curly braces, and can be renamed freely.

// logger.ts
export default function log(msg: string) {
  console.log(`[LOG] ${msg}`);
}

// app.ts
import myLogger from "./logger";
import { add, Point } from "./math";

myLogger("started");

Type-only imports

import type { Point } from "./math" imports only the type, which is erased entirely at compile time — nothing extra ships in the output JS.

Quick check: How many `export default` statements can one file have?

• At most one
• Unlimited
• Exactly one per interface