✅ 1. Core Node.js Concepts - Modules

Question 1

What is the syntax for importing named exports in ES6?

Answer 1

import { myFunction } from ‘./myModule.mjs’;

Question 2

What is the default module system in Node.js?

Answer 2

CommonJS (require() and module.exports) is the default module system in Node.js.

Question 3

What is the difference between CommonJS and ES6 modules?

Answer 3

• CommonJS: Uses require() and module.exports.
• ES6: Uses import and export.

Question 4

What file extension is required for ES6 modules in Node.js?

Answer 4

.mjs or add “type”: “module” in package.json.

Question 5

How do you export multiple functions in CommonJS?

Answer 5

module.exports = {
add,
subtract
};

Question 6

How do you export multiple functions in ES6 modules?

Answer 6

export { add, subtract };

Question 7

What is the output of this CommonJS code?
const math = require(‘./math’);
console.log(math.add(2, 3));

Answer 7

The output is the result of math.add() if the math module exports an add function.

Question 8

What is the output of this ES6 module code?
import { add } from ‘./math.mjs’;
console.log(add(2, 3));

Answer 8

The output is 5 if the add function is properly exported.

Question 9

What is the difference between require() and import in terms of execution?

Answer 9

• require() is synchronous.
• import is asynchronous.

Question 10

How do you import a default export in ES6 modules?

Answer 10

import myModule from ‘./myModule.mjs’;

Question 11

How do you import a default export in CommonJS?

Answer 11

const myModule = require(‘./myModule’);

Question 12

What is the difference between module.exports and exports in CommonJS?

Answer 12

• module.exports: The actual exported object.
• exports: A shortcut reference to module.exports.

Question 13

What is tree-shaking in ES6 modules?

Answer 13

It is the process of removing unused exports during bundling to optimize the code.

Question 14

What is the output of this code?
console.log(module);

Answer 14

It displays the current module object with properties like exports, id, and filename.

Question 15

How do you dynamically import a module in ES6?

Answer 15

const module = await import(‘./math.mjs’);

Question 16

What is the benefit of using ES6 modules over CommonJS?

Answer 16

• Asynchronous loading.
• Static analysis for better optimization.
• Tree-shaking support.

Question 17

What is the output of this ES6 code?
export default function greet() {
console.log(‘Hello’);
}

Answer 17

It exports the greet function as the default export.

Question 18

What happens if you reassign exports in CommonJS?

Answer 18

It breaks the module export. Use module.exports instead:
exports = { name: ‘test’ }; // Invalid
module.exports = { name: ‘test’ }; // Correct

Question 19

How do you use import syntax with CommonJS modules?

Answer 19

You cannot directly use import with CommonJS unless you add “type”: “module” in package.json.

Question 20

What is the output of this code?
module.exports = () => console.log(‘Hello’);

Answer 20

Exports an anonymous function that logs Hello.

Question 21

How do you handle circular dependencies in Node.js modules?

Answer 21

• Refactor code to avoid circular references.
• Use lazy loading or import().

Question 22

What is the output of this code using CommonJS?
const myModule = require(‘./myModule’);
console.log(myModule);

Answer 22

Logs the exported object or function from myModule.

Question 23

What is the output of this code using ES6?
import * as myModule from ‘./myModule.mjs’;
console.log(myModule);

Answer 23

Logs an object with all named exports from myModule.

Question 24

How do you mix import and require() in the same file?

Answer 24

You cannot mix them. Use either CommonJS or ES6 module syntax.

Question 25

What is the benefit of using import() over require()?

Answer 25

import() is asynchronous and supports dynamic loading.

Question 26

How do you mark a project as ES6 modules?

Answer 26

Add the following in package.json: json
“type”: “module”

Question 27

What is the output of this code?
const myModule = require(‘./myModule’);
console.log(typeof myModule);

Answer 27

The output is the data type of the exported value.

Question 28

How do you handle backward compatibility between CommonJS and ES6 modules?

Answer 28

• Use Babel or TypeScript for compatibility.
• Use .mjs for ES6 and .cjs for CommonJS files.

Question 29

What is the output of this code?
import { add } from ‘./math.mjs’;
console.log(typeof add);

Answer 29

Logs the data type of the add export.

Question 30

How do you import everything from a module in ES6?

Answer 30

import * as utils from ‘./utils.mjs’;