What is the primary purpose of the RouterOutlet directive in Angular?

  • To define a route configuration.
  • To create a navigation link.
  • To act as a placeholder for route content.
  • To configure HTTP requests.
The primary purpose of the RouterOutlet directive in Angular is to act as a placeholder for route content. It is used in the template to determine where the routed components should be displayed within the layout. This is essential for rendering the correct component when navigating between routes. The other options do not accurately describe the role of RouterOutlet in Angular.

If a service is provided in a lazy-loaded module's providers array, when will the service instance be created?

  • When the application starts.
  • When the lazy-loaded module is loaded.
  • When the service is explicitly requested using a constructor.
  • When the service is imported in the root module.
If a service is provided in a lazy-loaded module's providers array, the service instance will be created when the lazy-loaded module is loaded. Lazy-loaded modules are loaded on-demand, so their services are also instantiated when the module is accessed. This can help reduce unnecessary service instantiation and improve application performance.

In which scenarios would you consider using ChangeDetectionStrategy.OnPush?

  • When the component depends on parent component data changes.
  • When the component has frequent, unrelated changes.
  • When the component is rarely used in the application.
  • When the component needs to check for changes on every interaction.
You would consider using ChangeDetectionStrategy.OnPush in scenarios where the component's updates depend on changes in its parent component. This strategy is beneficial when you want to optimize performance by reducing unnecessary change detection cycles. It's not typically used when a component needs to check for changes on every interaction or when it's rarely used.

What's the primary difference between the switchMap and mergeMap operators?

  • switchMap and mergeMap are identical and can be used interchangeably.
  • switchMap and mergeMap are used for completely different purposes and cannot be compared.
  • switchMap cancels the previous inner observable when a new one arrives, while mergeMap concurrently processes all inner observables.
  • switchMap processes all inner observables concurrently, while mergeMap cancels the previous inner observable when a new one arrives.
The primary difference is that switchMap cancels the previous inner observable when a new one arrives. In contrast, mergeMap concurrently processes all inner observables it receives. This behavior makes switchMap useful for scenarios where you want to ensure only the latest inner observable result is considered, while mergeMap retains all results from concurrently executing inner observables.

Which change detection strategy checks the component only when its input properties change?

  • ChangeWhenInputChanges
  • CheckOnce
  • Default
  • OnPush
The change detection strategy that checks the component only when its input properties change is "ChangeWhenInputChanges." This strategy is commonly referred to as "OnPush." When using this strategy, Angular will recheck a component only when its input properties change, improving performance by reducing unnecessary checks on components that haven't received new input data.

The lifecycle hook ngAfterViewInit is specifically related to a component's child ________.

  • Directive
  • Element
  • Module
  • Template
The lifecycle hook ngAfterViewInit is specifically related to a component's child template. This hook is called after Angular has fully initialized a component's view and any child views it contains. It allows you to interact with the template and its elements once they are ready for manipulation.

Which Route Guard allows you to check whether a user can activate a particular route?

  • CanActivate
  • CanActivateChild
  • CanDeactivate
  • CanLoad
The 'CanActivate' Route Guard is used to check whether a user can activate a particular route. It's commonly used for protecting routes based on authentication or other conditions. This guard determines if a user has permission to access a specific route and is typically used to secure routes in Angular applications. The other guards have different roles, such as 'CanActivateChild' for protecting child routes and 'CanDeactivate' for confirming navigation away from a component.

When making an HTTP request using the HttpClient, what type of object is returned?

  • Object
  • Observable
  • Promise
  • Response
When making an HTTP request using HttpClient, an Observable object is returned. Observables are used to handle asynchronous data streams and provide features like error handling and transformation, making them well-suited for managing HTTP responses.

In Angular, to define routes for an application, you typically create an array of ________ objects.

  • Component
  • Module
  • Route
  • RouterModule
In Angular, to define routes for an application, you typically create an array of Route objects. These objects define the mapping between routes and components, specifying which component should be displayed when a particular route is navigated to. The RouterModule is indeed used to set up the routing configuration in an Angular application, but it's not an array. Components and modules are essential parts of Angular, but they are not used directly to define routes.

Why is it recommended to use immutable data structures with the OnPush change detection strategy?

  • Immutable data structures are Angular's requirement.
  • Immutable data structures are easier to use.
  • Immutable data structures are faster.
  • Immutable data structures help avoid side effects.
It is recommended to use immutable data structures with the "OnPush" change detection strategy because immutable data structures help avoid side effects. In Angular, when you change an input property's value, it triggers change detection. Using mutable objects can lead to unintended changes and unexpected behavior. Immutable data structures ensure that once a value is set, it remains unchanged, making it easier to reason about component behavior and performance optimization.