Lazy loading modules with routes in Angular - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to lazy load the AdminModule in Angular routing.

Angular

const routes: Routes = [
  { path: 'admin', loadChildren: () => import('./admin/admin.module').[1] }
];

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

Afinally(m => m.AdminModule)

Bcatch(m => m.AdminModule)

Cthen(m => m.AdminModule)

Dload(m => m.AdminModule)

Attempts:

3 left

💡 Hint

Common Mistakes

Using catch() or finally() instead of then().

Trying to call load() which is not a function here.

Lazy loading uses import() with then() to load the module and return it.

2fill in blank

medium

Complete the code to define a route that lazy loads the UserModule.

Angular

const routes: Routes = [
  { path: 'user', [1]: () => import('./user/user.module').then(m => m.UserModule) }
];

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

Acomponent

BredirectTo

Cchildren

DloadChildren

Attempts:

3 left

💡 Hint

Common Mistakes

Using component instead of loadChildren.

Using redirectTo which is for redirects.

The loadChildren property is used to lazy load a module in Angular routes.

3fill in blank

hard

Fix the error in the lazy loading syntax for the AdminModule route.

Angular

const routes: Routes = [
  { path: 'admin', loadChildren: () => import('./admin/admin.module').[1] }
];

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

AAdminModule

Bthen(m => m.AdminModule)

Ccatch(m => m.AdminModule)

Dfinally(m => m.AdminModule)

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to access the module directly without then().

Using catch() or finally() incorrectly.

The import returns a promise, so you must use then() to access the module.

4fill in blank

hard

Fill both blanks to create a lazy loaded route for the SettingsModule with path 'settings'.

Angular

const routes: Routes = [
  { path: [1], loadChildren: () => import('./settings/settings.module').[2] }
];

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

A'settings'

Bthen(m => m.SettingsModule)

Ccatch(m => m.SettingsModule)

D'setting'

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong path string like 'setting'.

Using catch() instead of then().

The path should be the string 'settings' and lazy loading uses then(m => m.SettingsModule).

5fill in blank

hard

Fill all three blanks to define a lazy loaded route with path 'profile', loading ProfileModule, and adding a route guard 'AuthGuard'.

Angular

const routes: Routes = [
  { path: [1], loadChildren: () => import('./profile/profile.module').[2], canActivate: [[3]] }
];

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

A'profile'

Bthen(m => m.ProfileModule)

CAuthGuard

D'profiles'

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong path string like 'profiles'.

Forgetting to use then() after import.

Not adding the guard or misspelling it.

The path is 'profile', lazy loading uses then(m => m.ProfileModule), and the guard is AuthGuard.

Practice

1. What is the main purpose of lazy loading modules in Angular routing?

easy

A. To preload all modules when the app starts

B. To load modules only when the user navigates to their route

C. To load modules in alphabetical order

D. To load all modules at once for faster navigation

Solution

1. Step 1: Understand lazy loading concept

   Lazy loading means delaying the loading of a module until it is needed, usually when the user navigates to a route that requires it.

2. Step 2: Identify the purpose in routing

   In Angular routing, lazy loading helps improve app speed by loading modules only on demand, not all at once.

3. Final Answer:

   To load modules only when the user navigates to their route -> Option B

4. Quick Check:

   Lazy loading = load on demand [OK]

Hint: Lazy loading means load modules only when needed [OK]

Common Mistakes:

• Thinking lazy loading loads all modules at start
• Confusing lazy loading with preloading
• Assuming lazy loading loads modules alphabetically

2. Which of the following is the correct syntax to lazy load a module named AdminModule in Angular routes?

easy

A. { path: 'admin', loadChildren: import('./admin/admin.module') }

B. { path: 'admin', loadChildren: './admin/admin.module#AdminModule' }

C. { path: 'admin', component: AdminModule }

D. { path: 'admin', loadChildren: () => import('./admin/admin.module').then(m => m.AdminModule) }

Solution

1. Step 1: Recall Angular lazy loading syntax

   Angular uses dynamic import with a function returning a promise that resolves to the module class.

2. Step 2: Match syntax to options

   { path: 'admin', loadChildren: () => import('./admin/admin.module').then(m => m.AdminModule) } uses the correct arrow function with import and then to get AdminModule. { path: 'admin', loadChildren: './admin/admin.module#AdminModule' } is old deprecated string syntax. Options C and D are incorrect usage.

3. Final Answer:

   { path: 'admin', loadChildren: () => import('./admin/admin.module').then(m => m.AdminModule) } -> Option D

4. Quick Check:

   Dynamic import with arrow function = correct syntax [OK]

Hint: Use arrow function with import().then() for lazy loading [OK]

Common Mistakes:

• Using deprecated string syntax for loadChildren
• Assigning component instead of loadChildren
• Omitting the arrow function wrapper

3. Given this route configuration snippet:

{ path: 'shop', loadChildren: () => import('./shop/shop.module').then(m => m.ShopModule) }

What happens when the user navigates to /shop for the first time?

medium

A. The ShopModule is already loaded at app start, so navigation is instant

B. Navigation fails because loadChildren requires a component

C. The ShopModule is loaded asynchronously and its routes are activated

D. The entire app reloads to load ShopModule

Solution

1. Step 1: Understand lazy loading behavior on navigation

   When navigating to a lazy loaded route for the first time, Angular loads the module asynchronously.

2. Step 2: Identify what happens on first navigation

   The ShopModule is fetched, loaded, and its routes become active, enabling the user to see the shop page.

3. Final Answer:

   The ShopModule is loaded asynchronously and its routes are activated -> Option C

4. Quick Check:

   First navigation triggers async module load [OK]

Hint: First visit loads module asynchronously, not at app start [OK]

Common Mistakes:

• Assuming module loads at app start
• Confusing loadChildren with component property
• Thinking app reloads on lazy load

4. Identify the error in this Angular route configuration for lazy loading:

{ path: 'dashboard', loadChildren: './dashboard/dashboard.module#DashboardModule' }

medium

A. Using string syntax for loadChildren is deprecated and causes errors

B. Missing component property for the route

C. Path should be capitalized as 'Dashboard'

D. loadChildren should be a component, not a string

Solution

1. Step 1: Check loadChildren syntax

   The string syntax with '#ModuleName' is deprecated in Angular and may cause errors in recent versions.

2. Step 2: Identify correct syntax

   Modern Angular requires loadChildren to be a function returning a dynamic import promise, not a string.

3. Final Answer:

   Using string syntax for loadChildren is deprecated and causes errors -> Option A

4. Quick Check:

   Use dynamic import function, not string [OK]

Hint: Avoid string syntax; use dynamic import function [OK]

Common Mistakes:

• Using old string syntax for loadChildren
• Confusing component and loadChildren properties
• Ignoring case sensitivity in paths

5. You want to lazy load a feature module ProfileModule only when the user navigates to /profile. The module has child routes. Which is the best way to configure the main app routing to achieve this and ensure accessibility and performance?

hard

A. { path: 'profile', loadChildren: () => import('./profile/profile.module').then(m => m.ProfileModule), canActivate: [AuthGuard] }

B. { path: 'profile', component: ProfileModule }

C. { path: 'profile', loadChildren: () => import('./profile/profile.module').then(m => m.ProfileModule) }

D. { path: 'profile', loadChildren: './profile/profile.module#ProfileModule' }

Solution

1. Step 1: Identify modern lazy loading syntax

   The correct syntax uses dynamic import with an arrow function returning a promise: loadChildren: () => import('./profile/profile.module').then(m => m.ProfileModule).

2. Step 2: Consider best practices for accessibility and performance

   For protected features like a user profile, adding canActivate: [AuthGuard] ensures secure access while lazy loading maintains performance.

3. Step 3: Eliminate incorrect configurations

   Using component property fails for modules with child routes. String syntax like './profile/profile.module#ProfileModule' is deprecated.

4. Final Answer:

   { path: 'profile', loadChildren: () => import('./profile/profile.module').then(m => m.ProfileModule), canActivate: [AuthGuard] } -> Option A

5. Quick Check:

   Lazy load with guard for best practice [OK]

Hint: Lazy load with import and add guards for security [OK]

Common Mistakes:

• Using component instead of loadChildren for modules
• Using deprecated string syntax
• Forgetting route guards for protected routes