Modules

Question 1

Why are modules needed?

Answer 1

1) Isolation
2) File system organization
3) Reuse

Question 2

Modules history

Answer 2

1) IIFE
(const a = 2; APP.number = a)()
Only works in the browser

2) require
module.exports = {a, b}
const {a,b} = require(some.js)
Only works in Node, and in the browser it is used only for assembly. Webpack actually also assembles everything on Node

3) ES modules
export
import

Question 3

Differences between CommonJS and ES modules

Answer 3

CommonJS Modules:
1) Require anywhere
2) Can be used in conditions
3) Loads the entire module, even if we import a small part
4) Synchronous module loading, can block the thread

ES Modules:
1) Imports must always be at the top level
2) Cannot be used in conditions (except asynchronous)
3) Selectively loads parts of their module
4) Asynchronous module loading

Question 4

How to use ES modules in Node?

Answer 4

1) Work with .mjs files
2) In package.json write type: “module”
3) Pass node argument –input-type=module

Question 5

How is modules wrapped in Node?

Answer 5

All files wrapped with anonimous function -

function (exports, require, module, __filename, __dirname) {}