Effects for side effects in Angular - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the EffectsModule in Angular.

Angular

import { [1] } from '@ngrx/effects';

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

AEffectsModules

BEffectModule

CEffectModules

DEffectsModule

Attempts:

3 left

💡 Hint

Common Mistakes

Using singular 'EffectModule' instead of plural 'EffectsModule'.

Adding extra 's' or misspelling the module name.

The correct import is EffectsModule from '@ngrx/effects'.

2fill in blank

medium

Complete the code to create an effect that listens for a 'loadItems' action.

Angular

loadItems$ = createEffect(() => this.actions$.pipe(ofType([1]), /* side effect here */));

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

AloadItemsAction

BloadItems

Cload_items

DLoadItems

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect casing or underscores in action names.

Adding 'Action' suffix when not defined.

The ofType operator listens for the exact action name, which is loadItems.

3fill in blank

hard

Fix the error in the effect to correctly dispatch a new action after a side effect.

Angular

loadItems$ = createEffect(() => this.actions$.pipe(ofType(loadItems), switchMap(() => this.api.getItems().pipe(map(items => [1])))));

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

AloadItemsSuccess({ items })

BloadItemsSuccess = items

CloadItemsSuccess(items: items)

DloadItemsSuccess(items)

Attempts:

3 left

💡 Hint

Common Mistakes

Passing payload directly without object.

Using assignment instead of function call.

The correct way to dispatch an action with payload is calling the action creator with an object: loadItemsSuccess({ items }).

4fill in blank

hard

Fill both blanks to create an effect that handles errors by dispatching a failure action.

Angular

loadItems$ = createEffect(() => this.actions$.pipe(ofType(loadItems), switchMap(() => this.api.getItems().pipe(map(items => loadItemsSuccess({ items })), [1](error => of([2]))))));

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

AcatchError

BloadItemsFailure({ error })

CloadItemsFail({ error })

DcatchErrors

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect operator name like 'catchErrors'.

Using wrong failure action name.

Use catchError to catch errors and dispatch loadItemsFailure with the error.

5fill in blank

hard

Complete the code to define an effect that does not dispatch any action but performs a side effect.

Angular

logAction$ = createEffect(() => this.actions$.pipe(ofType(logEvent), tap(() => console.log('Event logged'))), { {{BLANK_1}: false,} });

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

Adispatch

B,

C}

D;

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting the dispatch option or setting it to true.

Syntax errors with missing commas or braces.

Set dispatch: false in the effect options object to indicate no action is dispatched.

Practice

1. What is the main purpose of Effects in Angular applications?

easy

A. To define routes in the application

B. To style components dynamically

C. To handle side tasks like data fetching or logging outside components

D. To manage component templates

Solution

1. Step 1: Understand the role of Effects

   Effects are designed to handle side effects such as data fetching or logging, which are tasks outside the component's direct responsibilities.

2. Step 2: Compare with other options

   Styling, template management, and routing are handled by other Angular features, not Effects.

3. Final Answer:

   To handle side tasks like data fetching or logging outside components -> Option C

4. Quick Check:

   Effects = side tasks handler [OK]

Hint: Effects manage side tasks outside components [OK]

Common Mistakes:

• Confusing Effects with component styling
• Thinking Effects manage routing
• Assuming Effects handle templates

2. Which of the following is the correct way to create an effect using Angular's createEffect function?

easy

A. const loadData$ = createEffect(() => { this.actions$.pipe(ofType(load), switchMap(() => fetchData())); });

B. const loadData$ = createEffect(() => this.actions$.pipe(ofType(load), switchMap(() => fetchData())));

C. const loadData$ = createEffect(this.actions$.pipe(ofType(load), switchMap(() => fetchData())));

D. const loadData$ = createEffect(() => this.actions$.pipe(ofType(load), map(() => fetchData())));

Solution

1. Step 1: Check the syntax of createEffect

   The createEffect function expects a function returning an observable, so it should be () => this.actions$.pipe(...).

2. Step 2: Verify operators used

   Using switchMap is correct for side effects that return new observables. const loadData$ = createEffect(() => this.actions$.pipe(ofType(load), switchMap(() => fetchData()))); uses this correctly.

3. Final Answer:

   const loadData$ = createEffect(() => this.actions$.pipe(ofType(load), switchMap(() => fetchData()))); -> Option B

4. Quick Check:

   createEffect needs a function returning observable [OK]

Hint: createEffect needs a function returning an observable [OK]

Common Mistakes:

• Passing observable directly instead of a function
• Using map instead of switchMap for async calls
• Not returning the observable inside createEffect

3. Given this effect code snippet:

loadData$ = createEffect(() => this.actions$.pipe(
  ofType(loadData),
  switchMap(() => this.api.getData()),
  map(data => loadDataSuccess({ data })),
  catchError(() => of(loadDataFailure()))
));

What happens when the loadData action is dispatched?

medium

A. The API call is ignored and no action is dispatched

B. The effect causes a syntax error and stops

C. Only loadDataFailure action is dispatched immediately

D. The API call is made, and on success, loadDataSuccess action is dispatched

Solution

1. Step 1: Understand the effect flow

   When loadData action is dispatched, the effect listens and triggers the API call via switchMap.

2. Step 2: Analyze success and error handling

   On success, map dispatches loadDataSuccess with data; on error, catchError dispatches loadDataFailure.

3. Final Answer:

   The API call is made, and on success, loadDataSuccess action is dispatched -> Option D

4. Quick Check:

   Effect triggers API and dispatches success or failure [OK]

Hint: Effects dispatch success or failure actions after API calls [OK]

Common Mistakes:

• Assuming no action is dispatched after API call
• Confusing map with catchError behavior
• Thinking effect causes syntax error

4. Identify the error in this effect code:

saveData$ = createEffect(() => this.actions$.pipe(
  ofType(saveData),
  switchMap(action => this.api.save(action.payload)),
  map(() => saveDataSuccess()),
  catchError(error => saveDataFailure({ error }))
));

medium

A. The catchError operator should return an observable

B. The switchMap should not use action parameter

C. The map operator must return the original action

D. The effect should not use createEffect function

Solution

1. Step 1: Check catchError usage

   The catchError operator must return an observable, but here it returns an action object directly.

2. Step 2: Correct catchError return

   Wrapping the action in of() makes it an observable, fixing the error.

3. Final Answer:

   The catchError operator should return an observable -> Option A

4. Quick Check:

   catchError must return observable [OK]

Hint: Always wrap catchError return in of() to return observable [OK]

Common Mistakes:

• Returning plain object instead of observable in catchError
• Misusing switchMap parameters
• Thinking map must return original action

5. You want to create an effect that listens for login actions, calls an API to authenticate, and then dispatches either loginSuccess or loginFailure. Additionally, you want to log every login attempt regardless of success or failure. Which approach correctly implements this using Angular Effects?

hard

A. Use two separate effects: one for API call with dispatch, another for logging with dispatch: false

B. Use one effect with switchMap for API call and tap for logging inside the same pipe

C. Use one effect with map for API call and catchError for logging

D. Use one effect with filter to block logging and API call

Solution

1. Step 1: Separate concerns for side effects

   Logging is a side effect that does not dispatch actions, so it should be in a separate effect with dispatch: false.

2. Step 2: API call effect dispatches success or failure

   The main effect handles the API call and dispatches loginSuccess or loginFailure accordingly.

3. Step 3: Final design

   Two effects keep code clean and responsibilities clear: one for API calls with dispatch, one for logging without dispatch.

4. Final Answer:

   Use two separate effects: one for API call with dispatch, another for logging with dispatch: false -> Option A

5. Quick Check:

   Separate effects for dispatching and logging [OK]

Hint: Use separate effects for dispatching and non-dispatching tasks [OK]

Common Mistakes:

• Combining logging and dispatching in one effect incorrectly
• Using map instead of switchMap for API calls
• Forgetting dispatch: false for logging effect