Why modules are used in Javascript - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to export a function named greet.

Javascript

export function [1]() { console.log('Hello!'); }

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

Ahello

Bgreet

CsayHello

Dwelcome

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different function name than 'greet'.

The function name to export is greet as required.

2fill in blank

medium

Complete the code to import the greet function from 'greetings.js'.

Javascript

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

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

AsayHello

Bhello

Cwelcome

Dgreet

Attempts:

3 left

💡 Hint

Common Mistakes

Importing a function name that was not exported.

The function greet is imported as it was exported from 'greetings.js'.

3fill in blank

hard

Fix the error in the code to correctly export a constant named PI.

Javascript

const PI = 3.14;
[1] PI;

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

Aexport

Bexports

Cexport default

Dmodule.exports

Attempts:

3 left

💡 Hint

Common Mistakes

Using CommonJS export syntax in ES modules.

Use export to export the constant in ES modules.

4fill in blank

hard

Fill both blanks to create a module that exports a function and imports another.

Javascript

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

export function [2]() {
  return [1](5, 3);
}

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

Aadd

Bsubtract

Cmultiply

Ddivide

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up function names for import and export.

The function add is imported and used inside the exported subtract function as per the code logic.

5fill in blank

hard

Fill all three blanks to create a module exporting a default function and importing named ones.

Javascript

import { [1], [2] } from './utils.js';

export default function [3]() {
  [1]();
  [2]();
}

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

AlogInfo

BlogError

ChandleLogs

DprocessData

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing default export with named imports.

The functions logInfo and logError are imported and called inside the default exported function handleLogs.

Practice

1. Why do JavaScript modules help in programming?

easy

A. They split code into smaller, manageable parts.

B. They make the code run faster.

C. They remove the need for variables.

D. They automatically fix bugs.

Solution

1. Step 1: Understand the purpose of modules

   Modules are designed to divide code into smaller pieces that are easier to manage.

2. Step 2: Compare options with module benefits

   Only splitting code into smaller parts matches the main use of modules.

3. Final Answer:

   They split code into smaller, manageable parts. -> Option A

4. Quick Check:

   Modules = smaller code parts [OK]

Hint: Modules break code into parts for easy management [OK]

Common Mistakes:

• Thinking modules speed up code automatically
• Believing modules remove variables
• Assuming modules fix bugs by themselves

2. Which of the following is the correct way to export a function named greet from a JavaScript module?

easy

A. export greet() {}

B. export function greet() {}

C. function export greet() {}

D. export = greet()

Solution

1. Step 1: Recall JavaScript export syntax

   The correct syntax to export a function is to write export function functionName() {}.

2. Step 2: Check each option

   Only export function greet() {} matches the correct syntax for exporting a function.

3. Final Answer:

   export function greet() {} -> Option B

4. Quick Check:

   Export function syntax = export function name() [OK]

Hint: Use 'export function name()' to export functions [OK]

Common Mistakes:

• Placing export after function keyword
• Using incorrect export assignment syntax
• Omitting the function keyword

3. What will be the output of the following code?

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

// file: main.js
import { add } from './math.js';
console.log(add(3, 4));

medium

A. 34

B. undefined

C. Error: add is not defined

D. 7

Solution

1. Step 1: Understand import and export usage

   The function add is exported from math.js and imported correctly in main.js.

2. Step 2: Calculate the function output

   Calling add(3, 4) returns 3 + 4 = 7, which is logged.

3. Final Answer:

   7 -> Option D

4. Quick Check:

   3 + 4 = 7 [OK]

Hint: Imported functions run normally if exported correctly [OK]

Common Mistakes:

• Forgetting to export the function
• Using wrong import syntax
• Expecting string concatenation instead of addition

4. Identify the error in this module usage:

// file: utils.js
export function greet() { console.log('Hello'); }

// file: app.js
import greet from './utils.js';
greet();

medium

A. Missing curly braces in import statement

B. Function greet is not exported

C. Wrong file path in import

D. greet is called without parentheses

Solution

1. Step 1: Check export and import syntax

   The function greet is exported as a named export, so import must use curly braces.

2. Step 2: Identify import statement error

   Importing without curly braces tries to import a default export, which does not exist here.

3. Final Answer:

   Missing curly braces in import statement -> Option A

4. Quick Check:

   Named exports need braces in import [OK]

Hint: Use braces for named imports, no braces for default [OK]

Common Mistakes:

• Confusing named and default exports
• Calling function without parentheses
• Incorrect file path usage

5. You want to organize a large JavaScript project by splitting code into modules. Which of these is NOT a benefit of using modules?

hard

A. They help avoid naming conflicts by keeping variables local.

B. They allow code reuse across different files.

C. They automatically optimize code performance.

D. They make code easier to maintain and understand.

Solution

1. Step 1: Review benefits of modules

   Modules help organize code, avoid conflicts, and allow reuse and maintenance.

2. Step 2: Identify the incorrect statement

   Modules do not automatically optimize performance; optimization is separate.

3. Final Answer:

   They automatically optimize code performance. -> Option C

4. Quick Check:

   Modules organize, not optimize code [OK]

Hint: Modules organize and reuse code, not speed it up automatically [OK]

Common Mistakes:

• Assuming modules improve speed automatically
• Confusing code organization with performance
• Ignoring variable scope benefits