Default exports vs named exports in Typescript - Hands-On Comparison

Default exports vs named exports

📖 Scenario: You are building a small TypeScript project with two modules. One module will export a function as a default export, and the other module will export multiple functions as named exports. You will learn how to create and use both default and named exports.

🎯 Goal: Create a TypeScript project with one module using a default export and another module using named exports. Then import and use these exports in a main file.

📋 What You'll Learn

Create a module file greetDefault.ts with a default exported function called greetDefault that returns the string 'Hello from default export!'.

Create a module file greetNamed.ts with two named exported functions called greetMorning and greetEvening that return 'Good morning!' and 'Good evening!' respectively.

Create a main file main.ts that imports the default export from greetDefault.ts and the named exports from greetNamed.ts.

Call all three functions in main.ts and print their returned strings.

💡 Why This Matters

🌍 Real World

Modules with default and named exports are common in TypeScript projects to organize code and share functionality between files.

💼 Career

Understanding how to use default and named exports is essential for working on modern TypeScript and JavaScript codebases in professional development.

1

Create default export function

Create a file called greetDefault.ts. Inside it, write a function called greetDefault that returns the string 'Hello from default export!'. Export this function as the default export using export default greetDefault.

Typescript

# Create the function greetDefault and export it as default
# Your code here

Hint

Use export default after defining the function to export it as default.

2

Create named export functions

Create a file called greetNamed.ts. Inside it, write two functions: greetMorning that returns 'Good morning!' and greetEvening that returns 'Good evening!'. Export both functions as named exports using export function.

Typescript

# Create two named exported functions greetMorning and greetEvening
# Your code here

Hint

Use export function before each function to export them by name.

3

Import exports in main file

Create a file called main.ts. Import the default export from greetDefault.ts as greetDefault. Also import the named exports greetMorning and greetEvening from greetNamed.ts. Use the import syntax: import greetDefault from './greetDefault' and import { greetMorning, greetEvening } from './greetNamed'.

Typescript

# Import greetDefault as default import
# Import greetMorning and greetEvening as named imports
# Your code here

Hint

Use default import syntax without braces and named import syntax with braces.

4

Call functions and print results

In main.ts, call the functions greetDefault(), greetMorning(), and greetEvening(). Print their returned strings using console.log.

Typescript

# Call greetDefault(), greetMorning(), greetEvening() and print their results
# Your code here

Hint

Use console.log to print each function's return value on its own line.

Practice

1. What is the main difference between default export and named exports in TypeScript?

easy

A. Default export requires curly braces when importing, named exports do not.

B. Default export allows exporting one main value per file, named exports allow multiple exports by name.

C. Named exports can only export functions, default exports can only export objects.

D. Default exports are deprecated in TypeScript, named exports are preferred.

Solution

1. Step 1: Understand default export purpose

   Default export is designed to export a single main value from a file, like a main function or class.

2. Step 2: Understand named exports purpose

   Named exports allow exporting multiple values by their names, so you can import only what you need.

3. Final Answer:

   Default export allows exporting one main value per file, named exports allow multiple exports by name. -> Option B

4. Quick Check:

   Default export = one main, Named exports = multiple [OK]

Hint: Default = one main export, named = many exports by name [OK]

Common Mistakes:

• Confusing import syntax for default and named exports
• Thinking default export can export multiple items
• Assuming named exports require default keyword

2. Which of the following is the correct syntax to import a default export from a module named utils.ts?

easy

A. import utils from './utils';

B. import { utils } from './utils';

C. import * as utils from './utils';

D. import utils = require('./utils');

Solution

1. Step 1: Recall default import syntax

   Default exports are imported without curly braces using the syntax: import name from 'module'.

2. Step 2: Check options for correct syntax

   import utils from './utils'; matches this syntax exactly, importing the default export as utils.

3. Final Answer:

   import utils from './utils'; -> Option A

4. Quick Check:

   Default import has no braces [OK]

Hint: Default imports have no curly braces [OK]

Common Mistakes:

• Using curly braces for default imports
• Confusing import * as with default import
• Using require syntax in ES modules

3. Given the following module mathUtils.ts:

export default function add(a: number, b: number) { return a + b; }
export function multiply(a: number, b: number) { return a * b; }

What will be the output of this code?

import add, { multiply } from './mathUtils';
console.log(add(2, 3));
console.log(multiply(2, 3));

medium

A. NaN and 6

B. Syntax error

C. 5 and undefined

D. 5 and 6

Solution

1. Step 1: Understand import statements

   The default export function add is imported without braces, and the named export multiply is imported with braces.

2. Step 2: Evaluate function calls

   add(2, 3) returns 5, and multiply(2, 3) returns 6, so console logs 5 and 6.

3. Final Answer:

   5 and 6 -> Option D

4. Quick Check:

   Default + named import works = 5 and 6 [OK]

Hint: Default import no braces, named import with braces [OK]

Common Mistakes:

• Importing default export with braces
• Calling undefined functions due to wrong import
• Confusing output values

4. Consider this code snippet:

export default function greet() { return 'Hello'; }
export function greet() { return 'Hi'; }

What is the problem here?

medium

A. There is no problem; this code works fine.

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

C. You cannot have two functions with the same name exported, even if one is default.

D. Named exports cannot be functions.

Solution

1. Step 1: Identify duplicate function names

   Both the default export and named export use the same function name greet, which causes a conflict.

2. Step 2: Understand export rules

   Exports must have unique names; default export can be anonymous or named but cannot clash with named exports.

3. Final Answer:

   You cannot have two functions with the same name exported, even if one is default. -> Option C

4. Quick Check:

   Duplicate export names cause error [OK]

Hint: Default and named exports cannot share the same name [OK]

Common Mistakes:

• Assuming default export must be anonymous
• Thinking named exports can't be functions
• Ignoring duplicate export names

5. You have a file shapes.ts exporting multiple shapes and a default export for the main shape:

export interface Circle { radius: number; }
export interface Square { side: number; }
const defaultShape = { type: 'circle', radius: 5 };
export default defaultShape;

How would you import both the default shape and the Square interface correctly in another file?

hard

A. import defaultShape, { Square } from './shapes';

B. import { defaultShape, Square } from './shapes';

C. import { defaultShape } from './shapes'; import Square from './shapes';

D. import * as shapes from './shapes';

Solution

1. Step 1: Import default export without braces

   The default export defaultShape is imported without curly braces.

2. Step 2: Import named export with braces

   The named export Square interface is imported with curly braces.

3. Final Answer:

   import defaultShape, { Square } from './shapes'; -> Option A

4. Quick Check:

   Default no braces, named with braces [OK]

Hint: Default import no braces, named imports with braces [OK]

Common Mistakes:

• Using braces for default import
• Trying to import default as named
• Confusing import * as with default import