Default exports in Javascript - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to export the function as the default export.

Javascript

function greet() {
  console.log('Hello!');
}

export [1] greet;

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

Aconst

Bdefault

Clet

Dvar

Attempts:

3 left

💡 Hint

Common Mistakes

Using variable declaration keywords like const or let instead of 'default'.

Forgetting to write 'default' when exporting a single main value.

The keyword default is used to export a single value or function as the default export from a module.

2fill in blank

medium

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

Javascript

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

[1]();

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

Agreet

B{ greet }

C* as greet

D{ default }

Attempts:

3 left

💡 Hint

Common Mistakes

Using curly braces around the default import name.

Using import * as syntax for default imports.

When importing a default export, you use a simple name without curly braces.

3fill in blank

hard

Fix the error in the export statement to correctly export the default value.

Javascript

const message = 'Hi there!';

export [1] = message;

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

Adefault

Bconst

Clet

Dvar

Attempts:

3 left

💡 Hint

Common Mistakes

Using an equals sign (=) after export default.

Trying to declare a variable with export default.

The correct syntax for default export of a value is export default value; without an equals sign.

4fill in blank

hard

Fill both blanks to export a default arrow function and import it correctly.

Javascript

export [1] () => {
  console.log('Welcome!');
};

import greet from './welcome.js';
greet();

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

Adefault

Bfunction

Cconst

Dlet

Attempts:

3 left

💡 Hint

Common Mistakes

Using variable declarations like const or let directly with export default without assignment.

Omitting the function keyword when exporting a function.

To export a default function expression, use export default function. The import uses the default import syntax.

5fill in blank

hard

Fill all three blanks to export a default class and import it with a new name.

Javascript

export [1] class [2] {
  constructor() {
    console.log('Created');
  }
}

import [3] from './MyClass.js';
const obj = new [3]();

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

Adefault

BMyClass

CRenamedClass

Dclass

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to write default in the export statement.

Trying to import default exports with curly braces.

Using the original class name instead of the renamed import.

Use export default class MyClass to export the class. When importing, you can rename the default import to any name you want.

Practice

1. What is a default export in JavaScript modules?

easy

A. A single main value or function exported from a file without curly braces when importing.

B. Multiple named values exported from a file using curly braces when importing.

C. A way to export variables only, not functions.

D. A special export that requires double curly braces when importing.

Solution

1. Step 1: Understand export types

   JavaScript modules can export multiple named items or one default item.

2. Step 2: Identify default export usage

   Default export is a single main export imported without curly braces.

3. Final Answer:

   A single main value or function exported from a file without curly braces when importing. -> Option A

4. Quick Check:

   Default export = single main export without braces [OK]

Hint: Default exports import without braces, named exports need braces [OK]

Common Mistakes:

• Confusing default export with named exports
• Using curly braces when importing default export
• Thinking default export can export multiple items

2. Which of the following is the correct syntax to export a default function named greet?

easy

A. default export function greet() {}

B. export function default greet() {}

C. export default function greet() {}

D. export greet default function() {}

Solution

1. Step 1: Recall default export syntax

   The correct syntax is to write export default followed by the function declaration.

2. Step 2: Check each option

   Only export default function greet() {} matches the correct syntax: export default function greet() {}.

3. Final Answer:

   export default function greet() {} -> Option C

4. Quick Check:

   export default + function name = correct syntax [OK]

Hint: Remember: 'export default' comes before function name [OK]

Common Mistakes:

• Placing 'default' after function name
• Using 'default export' instead of 'export default'
• Mixing order of keywords

3. Given the file math.js with content:

export default function add(a, b) { return a + b; }

What will be the output of this code?

import add from './math.js';
console.log(add(3, 4));

medium

A. undefined

B. 7

C. TypeError

D. NaN

Solution

1. Step 1: Understand import of default export

   The function add is exported as default and imported without braces correctly.

2. Step 2: Evaluate function call

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

3. Final Answer:

   7 -> Option B

4. Quick Check:

   Default import calls function correctly = 7 [OK]

Hint: Default export imports as named variable, call normally [OK]

Common Mistakes:

• Using curly braces when importing default export
• Expecting undefined because of wrong import
• Confusing default export with named export

4. Identify the error in this code snippet:

import { greet } from './hello.js';
export default function greet() { return 'Hi'; }

medium

A. Cannot import default export using curly braces.

B. Function cannot be named greet when exported default.

C. Missing semicolon after export statement.

D. Default export must be a variable, not a function.

Solution

1. Step 1: Check import syntax

   Importing default export must be done without curly braces, but here curly braces are used.

2. Step 2: Confirm export syntax

   Exporting default function named greet is valid, so no error there.

3. Final Answer:

   Cannot import default export using curly braces. -> Option A

4. Quick Check:

   Default import no braces, braces cause error [OK]

Hint: Default exports import without braces; braces mean named import [OK]

Common Mistakes:

• Using curly braces to import default export
• Thinking default export must be unnamed
• Assuming semicolon is mandatory for export

5. You have two files:

// file1.js
const value = 42;
export default value;

// file2.js
import val from './file1.js';
console.log(val);

How can you change file1.js to export both value as default and a named constant name with value 'Answer'?

hard

A. Cannot export default and named exports together in one file.

B. Change default export to named export for value and export name as default.

C. Use export default { value, name }; to export both.

D. Add export const name = 'Answer'; alongside default export.

Solution

1. Step 1: Understand export combinations

   JavaScript allows one default export and multiple named exports in the same file.

2. Step 2: Add named export alongside default

   Adding export const name = 'Answer'; exports a named constant while keeping default export.

3. Final Answer:

   Add export const name = 'Answer'; alongside default export. -> Option D

4. Quick Check:

   Default + named exports can coexist [OK]

Hint: Default export plus named exports can be in same file [OK]

Common Mistakes:

• Thinking default and named exports cannot coexist
• Trying to export multiple defaults
• Using object as default export to hold multiple values