Module lazy loading preview 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'

Athen(m => m.AdminModule)

Bcatch(m => m.AdminModule)

Cfinally(m => m.AdminModule)

Dload(m => m.AdminModule)

Attempts:

3 left

💡 Hint

Common Mistakes

Using catch instead of then causes errors.

Trying to call load which is not a function.

Use then(m => m.AdminModule) to load the module after import.

2fill in blank

medium

Complete the code to define a lazy loaded route for the UserModule.

Angular

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

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

Athen(m => m.UserModule)

BloadUserModule()

Ccatch(m => m.UserModule)

Dload(m => m.UserModule)

Attempts:

3 left

💡 Hint

Common Mistakes

Using a function call like loadUserModule() which is not valid here.

Using catch instead of then.

The then method accesses the exported module after dynamic import.

3fill in blank

hard

Fix the error in the lazy loading syntax for the SettingsModule.

Angular

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

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

Athen(m => m.settingsmodule)

Bthen(m => m.settingsModule)

Cthen(m => m.Settingsmodule)

Dthen(m => m.SettingsModule)

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase or incorrect casing for the module name.

Misspelling the module name.

Module names are case sensitive and usually PascalCase, so SettingsModule is correct.

4fill in blank

hard

Fill both blanks to correctly lazy load the ReportsModule with a path 'reports'.

Angular

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

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

Areports

Breport

Cthen(m => m.ReportsModule)

Dthen(m => m.ReportModule)

Attempts:

3 left

💡 Hint

Common Mistakes

Using singular 'report' instead of 'reports' for the path.

Incorrect casing in the module name.

The path should be 'reports' and the module name ReportsModule with correct casing.

5fill in blank

hard

Fill all three blanks to lazy load the DashboardModule with path 'dashboard' and enable preloading strategy.

Angular

import { RouterModule, Routes, [1] } from '@angular/router';

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

@NgModule({
  imports: [RouterModule.forRoot(routes, { preloadingStrategy: [1] })],
  exports: [RouterModule]
})
export class AppRoutingModule {}

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

APreloadAllModules

Bdashboard

Cthen(m => m.DashboardModule)

DNoPreloading

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to import the preloading strategy.

Using wrong path or module name casing.

Not setting preloadingStrategy in forRoot.

Use PreloadAllModules to preload lazy modules, path is 'dashboard', and module name is DashboardModule.

Practice

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

easy

A. To load modules only when they are needed, improving startup speed

B. To preload all modules at app start for faster navigation

C. To combine all modules into one big file for simplicity

D. To disable routing and load components manually

Solution

1. Step 1: Understand lazy loading concept

   Lazy loading means delaying the loading of parts of the app until they are needed, not all at once.

2. Step 2: Identify the benefit

   This reduces the initial load time and speeds up app startup by loading only essential code first.

3. Final Answer:

   To load modules only when they are needed, improving startup speed -> Option A

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
• Believing lazy loading disables routing

2. Which of the following is the correct syntax to lazy load a module named AdminModule located at ./admin/admin.module.ts in Angular routing?

easy

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

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

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

D. { path: 'admin', loadChildren: () => AdminModule }

Solution

1. Step 1: Recall Angular lazy loading syntax

   Since Angular 8+, lazy loading uses dynamic import syntax with loadChildren as a function returning a promise.

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 the module class.

3. Final Answer:

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

4. Quick Check:

   Dynamic import with arrow function = { path: 'admin', loadChildren: () => import('./admin/admin.module').then(m => m.AdminModule) } [OK]

Hint: Use dynamic import with arrow function for lazy loading [OK]

Common Mistakes:

• Using string syntax with # which is deprecated
• Assigning component instead of loadChildren
• Calling loadChildren without import

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 loaded immediately when the app starts

B. The ShopModule is never loaded and navigation fails

C. The ShopModule is loaded asynchronously only at navigation time

D. The ShopModule is loaded synchronously blocking the UI

Solution

1. Step 1: Understand lazy loading behavior on navigation

   With lazy loading, the module is not loaded at app start but only when the route is visited.

2. Step 2: Apply to given route

   When user navigates to '/shop', Angular triggers the dynamic import to load ShopModule asynchronously.

3. Final Answer:

   The ShopModule is loaded asynchronously only at navigation time -> Option C

4. Quick Check:

   Lazy load triggers on first navigation [OK]

Hint: Lazy loaded modules load on first route visit, not app start [OK]

Common Mistakes:

• Assuming module loads at app start
• Thinking navigation fails without preloading
• Believing loading blocks UI synchronously

4. Consider this incorrect route configuration:

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

What is the main issue with this code in Angular 17+?

medium

A. DashboardModule should be imported directly, not lazy loaded

B. Missing component property for the route

C. The path should be an array, not a string

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

Solution

1. Step 1: Identify deprecated syntax

   Angular versions 8+ require dynamic import syntax for lazy loading, not string with #.

2. Step 2: Explain impact

   Using string syntax causes build or runtime errors because Angular no longer supports it.

3. Final Answer:

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

4. Quick Check:

   String syntax deprecated = Using string syntax for loadChildren is deprecated and causes errors [OK]

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

Common Mistakes:

• Thinking component is required with loadChildren
• Confusing path type with string vs array
• Believing direct import is mandatory for lazy loading

5. You want to lazy load a feature module ProfileModule only when the user navigates to /profile. The module file is at ./profile/profile.module.ts. Which of the following route configurations correctly implements this with Angular 17+ standards and ensures accessibility and performance?

hard

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

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

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

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

Solution

1. Step 1: Use correct dynamic import syntax

   Angular 17+ requires loadChildren as a function returning a promise with dynamic import and then to access the module class.

2. Step 2: Verify accessibility and performance

   Lazy loading delays module load until navigation, improving performance. Using this syntax supports Angular's router and accessibility features.

3. Final Answer:

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

4. Quick Check:

   Dynamic import + then + lazy load = { path: 'profile', loadChildren: () => import('./profile/profile.module').then(m => m.ProfileModule) } [OK]

Hint: Always use dynamic import with then for lazy loading modules [OK]

Common Mistakes:

• Using deprecated string syntax
• Assigning component instead of loadChildren
• Missing .then() after import