A module is a JavaScript file that exports one or more values (objects, functions, or variables), using the export keyword.

For example, a file can export a variable:

const age = 18

export { age }

Or a function:

function calculate() {}

export { calculate }

test.js

You can then import this value in another file.

Suppose the file is named test.js and it’s in the same folder as the file you’re importing into. You’ll write

import { calculate } from './test.js'

And you can use that function as if it was written in the same file.

Notice I used ./ to say “current file’s folder”. If the file is in another folder, you’ll need a relative path, for example ../../test.js if it’s two subfolders up.

Using server-side JavaScript, when we get to that (Node / Deno / Bun), you’ll also see how to import from built-in modules and third-party modules.

Lessons in this unit:

0:	Introduction
1:	▶︎ Using import and export
2:	.mjs files
3:	Default exports
4:	Multiple exports
5:	Renaming exports
6:	Using the `script` tag