MEAN Angular Components and Services

Question 1

What decorator is used to define a service that can be injected into Angular components?

Accepted Answer

@Injectable()

Answer

@Injectable() marks a class as available for Angular's dependency injection system, and { providedIn: 'root' } makes it a singleton app-wide.

Question 2

What is Angular's Change Detection strategy `OnPush` used for?

Accepted Answer

Improves performance by only checking a component when its inputs change or events fire

Answer

ChangeDetectionStrategy.OnPush tells Angular to skip change detection for a component unless its @Input references change, an event occurs, or an Observable emits.

Question 3

Which Angular lifecycle hook is called after the component's view and child views are initialized?

Accepted Answer

ngAfterViewInit

Answer

ngAfterViewInit is called once after Angular finishes initializing the component's view and all child views, making it safe to interact with ViewChild references.

Question 4

What is the purpose of Angular's `@ViewChild` decorator?

Accepted Answer

Gets a reference to a child component, directive, or DOM element in the template

Answer

@ViewChild queries the component's view for a matching element or component and injects a reference into a component property.

Question 5

What does the Angular `async` pipe do in a template?

Accepted Answer

Subscribes to an Observable or Promise and returns the latest emitted value automatically

Answer

The async pipe subscribes to an Observable or Promise, returns the latest value, and automatically unsubscribes when the component is destroyed.

MEAN - Stack Development Practice Test

MEAN - Stack Development Practice Test

MEAN Angular Components and Services