Dynamic imports with types in Typescript - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to dynamically import the module.

Typescript

const module = await import([1]);

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

A'./myModule'

BmyModule

Cimport('./myModule')

D'myModule.js'

Attempts:

3 left

💡 Hint

Common Mistakes

Using a variable without quotes.

Trying to call import() inside import().

Using a file extension when not needed.

The import() function requires a string path to the module. So, './myModule' is correct.

2fill in blank

medium

Complete the code to import the type MyType from the module.

Typescript

import type { [1] } from './myModule';

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

AMyType

BmyType

Cmytype

DTypeMy

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase letters for type names.

Confusing variable names with type names.

TypeScript is case-sensitive. The type name is MyType exactly as declared.

3fill in blank

hard

Fix the error in the dynamic import with type assertion.

Typescript

const mod = await import('./myModule') as [1];

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

AMyType

BPromise<MyType>

CModuleType

Dtypeof import('./myModule')

Attempts:

3 left

💡 Hint

Common Mistakes

Asserting the type directly without typeof.

Using the type of the exported member instead of the module.

When asserting the type of a dynamically imported module, use typeof import('./myModule'), because the import returns a module object.

4fill in blank

hard

Fill both blanks to correctly type the dynamically imported function and call it.

Typescript

const [1] = (await import('./utils')).[2];
const result = await myFunc(5);

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

AmyFunc

Bcalculate

Ccompute

Dprocess

Attempts:

3 left

💡 Hint

Common Mistakes

Using different names for the variable and the imported function.

Using a function name that does not exist in the module.

The function exported is named myFunc. So both blanks should be myFunc to assign and call it correctly.

5fill in blank

hard

Fill all three blanks to dynamically import a module, extract a typed function, and call it with a typed argument.

Typescript

import type { [1] } from './math';
const { [2] } = await import('./math') as [3];
const output = [2](10);

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

ACalculateFn

Bcalculate

Ctypeof import('./math')

DMathType

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up type and function names.

Not using typeof import() for module typing.

First, import the type CalculateFn. Then extract the function calculate from the module. Finally, assert the module type with typeof import('./math').

Practice

1. What is the main benefit of using dynamic imports with types in TypeScript?

easy

A. They make the code run faster by compiling to machine code.

B. They load modules only when needed, improving app speed and type safety.

C. They automatically convert JavaScript to TypeScript.

D. They prevent any runtime errors without writing tests.

Solution

1. Step 1: Understand dynamic imports

   Dynamic imports load code only when it is needed, not all at once.

2. Step 2: Understand types with dynamic imports

   Using typeof import() adds type safety, helping catch errors early.

3. Final Answer:

   They load modules only when needed, improving app speed and type safety. -> Option B

4. Quick Check:

   Dynamic imports + types = faster and safer code [OK]

Hint: Dynamic imports delay loading; types keep code safe [OK]

Common Mistakes:

• Thinking dynamic imports compile code faster
• Confusing dynamic imports with automatic type conversion
• Believing dynamic imports prevent all runtime errors

2. Which of the following is the correct syntax to dynamically import a module named utils with types in TypeScript?

easy

A. const utils: typeof import('utils') = await import('utils');

B. const utils = await import('utils');

C. import utils from 'utils';

D. const utils = import('utils');

Solution

1. Step 1: Identify dynamic import syntax

   Dynamic imports use await import('module') inside async functions.

2. Step 2: Add type annotation

   Use const x: typeof import('module') to add types for the imported module.

3. Final Answer:

   const utils: typeof import('utils') = await import('utils'); -> Option A

4. Quick Check:

   Dynamic import with type annotation = const utils: typeof import('utils') = await import('utils'); [OK]

Hint: Use 'const x: typeof import() = await import()' [OK]

Common Mistakes:

• Omitting 'await' in dynamic import
• Using static import syntax for dynamic import
• Not adding type annotation for imported module

3. Consider this TypeScript code inside an async function:

const mod: typeof import('./math') = await import('./math');
const result = mod.add(2, 3);
console.log(result);

If ./math exports export function add(a: number, b: number) { return a + b; }, what will be the output?

medium

A. Type error at compile time

B. undefined

C. Runtime error: mod.add is not a function

D. 5

Solution

1. Step 1: Understand dynamic import with types

   The module is imported dynamically with correct typing, so mod.add is recognized as a function.

2. Step 2: Calculate the function call

   Calling mod.add(2, 3) returns 5, which is logged.

3. Final Answer:

   5 -> Option D

4. Quick Check:

   Dynamic import calls function correctly = 5 [OK]

Hint: Dynamic import with correct type calls function normally [OK]

Common Mistakes:

• Expecting undefined because of dynamic import
• Confusing runtime error with type error
• Forgetting to await the import

4. What is wrong with this TypeScript code snippet?

const mod: typeof import('./utils') = import('./utils');
console.log(mod.helper());

medium

A. Type annotation is incorrect; should not use typeof import().

B. Cannot call console.log inside async code.

C. Missing 'await' before import, so mod is a Promise, not the module.

D. Module './utils' does not exist.

Solution

1. Step 1: Check import usage

   Dynamic import returns a Promise, so it must be awaited to get the module.

2. Step 2: Identify error cause

   Without await, mod is a Promise, so calling mod.helper() causes an error.

3. Final Answer:

   Missing 'await' before import, so mod is a Promise, not the module. -> Option C

4. Quick Check:

   Dynamic import needs await to get module [OK]

Hint: Always await dynamic imports to get the module object [OK]

Common Mistakes:

• Forgetting to await dynamic import
• Misusing type annotation syntax
• Assuming import returns module directly

5. You want to dynamically import a module './config' that exports a default object with a property apiUrl. How do you correctly type and access apiUrl using dynamic imports in TypeScript?

hard

A. const config: typeof import('./config') = await import('./config'); console.log(config.default.apiUrl);

B. const config = await import('./config'); console.log(config.apiUrl);

C. const config: typeof import('./config') = await import('./config'); console.log(config.apiUrl);

D. const config = await import('./config'); console.log(config.default.apiUrl);

Solution

1. Step 1: Understand default exports in dynamic imports

   When a module exports default, it is accessed via the default property on the imported module object.

2. Step 2: Use type annotation and access property

   Typing with typeof import() is correct, and to get apiUrl, use config.default.apiUrl.

3. Final Answer:

   const config: typeof import('./config') = await import('./config'); console.log(config.default.apiUrl); -> Option A

4. Quick Check:

   Default export accessed via .default with type = const config: typeof import('./config') = await import('./config'); console.log(config.default.apiUrl); [OK]

Hint: Default exports accessed via .default after dynamic import [OK]

Common Mistakes:

• Accessing default export directly without .default
• Not using await with import
• Ignoring type annotation for imported module