Default exports vs named exports in Typescript - Quick Revision & Key Differences

Recall & Review

beginner

What is a default export in TypeScript?

A default export is a single value or entity that a module exports as its main thing. When importing, you can name it anything you want.

beginner

How do you import a default export?

You import a default export using the syntax: <code>import anyName from './module'</code>. The name can be anything you choose.

beginner

What are named exports?

Named exports allow a module to export multiple values by name. When importing, you must use the exact exported names inside curly braces.

beginner

How do you import named exports?

You import named exports using the syntax: <code>import { name1, name2 } from './module'</code>. The names must match exactly.

intermediate

Can a module have both default and named exports?

Yes, a module can have one default export and multiple named exports at the same time.

Which syntax imports a default export from a module?

A import * as myThing from './module'

B import { myThing } from './module'

C export default myThing

D import myThing from './module'

Default exports are imported without curly braces using any name you choose.

How do you import a named export called 'foo'?

A import { foo } from './module'

B import foo from './module'

C import * as foo from './module'

D export default foo

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

Can you rename a default import when importing?

A Yes, you can name it anything you want

B No, you must use the original name

C Only if you use 'as' keyword

D Only if the module exports multiple defaults

Default imports can be named anything during import.

Which statement is true about named exports?

A You can only have one named export per module

B Named exports must be imported with the exact exported names

C Named exports are imported without curly braces

D Named exports cannot be combined with default exports

Named exports require exact names and curly braces when importing.

Is this valid? export default function() {} and export const foo = 5; in the same file?

A No, you cannot mix default and named exports

B Only if you use 'export * from' syntax

C Yes, you can have one default and multiple named exports

D Only if you rename the default export

Modules can have one default export and many named exports together.

Explain the difference between default exports and named exports in TypeScript.

Think about how you import and name things from a module.

Describe how you would import both a default export and named exports from the same module.

Remember the syntax differences for default and named imports.

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