ES Modules

Real programs are split into many files called modules. Each module has its own scope: nothing inside it is visible to other files unless it is exported. export const add = ... creates a named export, imported with braces: import { add } from "./math.js". A file can also have one default export, imported without braces and under any name you like. This lesson is read and quiz, because modules are about several files working together.

// file: math.js
export const add = (a, b) => a + b;

export default function square(n) {
  return n * n;
}

// file: main.js
import square, { add } from "./math.js";

console.log(add(2, 3), square(4));

How it reads

• export const add is a named export: import it by its exact name in braces
• export default marks the file's main value: import it without braces
• Everything not exported stays private to its file

Cloud tip: Prefer named exports in shared code: editors can find them, and a typo in an import fails loudly instead of silently.