ES Modules import and export in Node.js - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the default export from a module.

Node.js

import [1] from './mathUtils.js';

Drag options to blanks, or click blank then click option'

Asum

Bmath

Ccalculate

Ddefault

Attempts:

3 left

💡 Hint

Common Mistakes

Using curly braces for default import

Trying to import without specifying a name

The default export can be imported with any name you choose. Here, sum is used as the local name.

2fill in blank

medium

Complete the code to import a named export called 'multiply' from a module.

Node.js

import { [1] } from './mathUtils.js';

Drag options to blanks, or click blank then click option'

Asum

Bmultiply

Cdefault

Dcalculate

Attempts:

3 left

💡 Hint

Common Mistakes

Using default import syntax for named exports

Misspelling the export name

Named exports must be imported using curly braces with the exact exported name.

3fill in blank

hard

Fix the error in the import statement to correctly import all named exports as an object.

Node.js

import * as [1] from './mathUtils.js';

Drag options to blanks, or click blank then click option'

Amath

Butils

Call

Dfunctions

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting the * as syntax

Using invalid variable names

Using * as math imports all named exports under the object math.

4fill in blank

hard

Fill both blanks to export a named function and a constant from a module.

Node.js

export function [1]() { return 42; }
export const [2] = 'hello';

Drag options to blanks, or click blank then click option'

AgetAnswer

Banswer

Cgreet

Dmessage

Attempts:

3 left

💡 Hint

Common Mistakes

Using the same name for both exports

Using invalid JavaScript identifiers

The function is named getAnswer and the constant is named message.

5fill in blank

hard

Fill all three blanks to create a module that exports a default function and two named constants.

Node.js

export default function [1]() {
  return [2] + [3];
}
export const pi = 3.14;
export const e = 2.71;

Drag options to blanks, or click blank then click option'

AcalculateSum

Bpi

Ce

Dsum

Attempts:

3 left

💡 Hint

Common Mistakes

Using undefined variables inside the function

Not matching the exported constant names

The default exported function is named sum and it returns the sum of pi and e.

Practice

1. What is the main purpose of using export and import in Node.js ES Modules?

easy

A. To create new variables inside a file

B. To run JavaScript code faster in Node.js

C. To convert JavaScript code into another language

D. To share code between different files by exporting and importing parts

Solution

1. Step 1: Understand the role of export

   The export keyword allows parts of a file (like functions or variables) to be shared with other files.

2. Step 2: Understand the role of import

   The import keyword is used to bring those shared parts into another file to use them.

3. Final Answer:

   To share code between different files by exporting and importing parts -> Option D

4. Quick Check:

   Export and import = share code [OK]

Hint: Export shares code, import uses it elsewhere [OK]

Common Mistakes:

• Thinking export/import changes code speed
• Confusing export with variable creation
• Believing export/import converts languages

2. Which of the following is the correct syntax to export a function named greet in an ES Module file?

easy

A. export function greet() {}

B. module.exports = greet;

C. export = greet;

D. exports.greet = function() {}

Solution

1. Step 1: Identify ES Module export syntax

   In ES Modules, use export function functionName() {} to export a function.

2. Step 2: Check other options for CommonJS syntax

   Options B and D use CommonJS style, not ES Modules. export = greet; is invalid syntax.

3. Final Answer:

   export function greet() {} -> Option A

4. Quick Check:

   ES Modules export function = export function [OK]

Hint: Use 'export function' for ES Modules exports [OK]

Common Mistakes:

• Using CommonJS syntax in ES Modules
• Writing invalid export syntax
• Confusing export default with named export

3. Given the following files, what will be logged when running node main.js?

// utils.js
export const value = 5;
export function double(x) { return x * 2; }

// main.js
import { value, double } from './utils.js';
console.log(double(value));

medium

A. 10

B. 5

C. undefined

D. SyntaxError

Solution

1. Step 1: Understand the imports and exports

   The file utils.js exports a constant value = 5 and a function double that multiplies input by 2.

2. Step 2: Trace the code in main.js

   It imports value and double, then calls double(value) which is double(5), returning 10.

3. Final Answer:

   10 -> Option A

4. Quick Check:

   double(5) = 10 [OK]

Hint: Import exports correctly, then call functions with values [OK]

Common Mistakes:

• Forgetting to add .js extension in import
• Confusing export default with named exports
• Expecting value instead of double(value)

4. What is the error in the following code snippet?

// math.js
export function add(a, b) { return a + b; }

// app.js
import { add } from './math';
console.log(add(2, 3));

medium

A. Function add is not exported correctly

B. Cannot import named exports with curly braces

C. Missing file extension in import statement

D. Using CommonJS syntax in ES Modules

Solution

1. Step 1: Check import statement syntax

   The import statement uses import { add } from './math'; but misses the .js extension required in Node.js ES Modules.

2. Step 2: Confirm export syntax is correct

   The function add is correctly exported with export function add(), so no error there.

3. Final Answer:

   Missing file extension in import statement -> Option C

4. Quick Check:

   Node.js ES Modules need file extensions [OK]

Hint: Always include .js extension in ES Module imports [OK]

Common Mistakes:

• Omitting file extensions in import paths
• Confusing CommonJS and ES Module syntax
• Assuming named exports don't use curly braces

5. You have two files:

// data.js
const secret = 'hidden';
export const visible = 'shown';
export default function getSecret() { return secret; }

// index.js
import getSecret, { visible } from './data.js';
console.log(visible);
console.log(getSecret());

What will be the output when running node index.js?

hard

A. SyntaxError due to mixed import syntax

B. shownhidden

C. shownundefined

D. hiddenshown

Solution

1. Step 1: Understand default and named exports

   getSecret is the default export function returning secret. visible is a named export with value 'shown'.

2. Step 2: Analyze import and console.log calls

   import getSecret, { visible } correctly imports default and named exports. Logging visible prints 'shown'. Calling getSecret() returns 'hidden'.

3. Final Answer:

   shown
   hidden -> Option B

4. Quick Check:

   Default + named import works = shown, hidden [OK]

Hint: Default import first, named imports in braces [OK]

Common Mistakes:

• Mixing default and named imports incorrectly
• Expecting secret variable to be exported directly
• Confusing order of import syntax