When creating custom form controls, the method used to write a new value to the view is ______.

changeValue()
patchValue()
setValue()
updateValue()

In Angular, when creating custom form controls, the method used to write a new value to the view is setValue(). This method allows you to set the value of a FormControl and update the view accordingly. It's a critical method for working with form controls in Angular.

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A client wants the ability to deep link to specific parts of your Angular application. What would you ensure to accommodate this requirement?

Utilizing Angular's RouterModule and configuring the application for hash-based routing.
Disabling routing in the Angular application to prevent deep linking.
Implementing a custom JavaScript solution for deep linking.
Creating static HTML pages for each deep linkable section of the application.

To accommodate the client's requirement of deep linking to specific parts of your Angular application, you should use Angular's RouterModule and configure the application for hash-based routing. This approach allows for deep linking by using URL fragments. The other options are not suitable for achieving deep linking in an Angular application.

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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.

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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.

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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.

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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.

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You want to test a component that has a dependency on another service, but you don't want to test the service's actual behavior. How would you approach this in Angular tests?

Create a mock service that provides controlled responses
Mock the component instead of the service
Use HttpClientTestingModule to mock HTTP service
Use the actual service for realistic testing

To isolate the component's behavior for testing, you should create a mock service that provides controlled responses. This allows you to focus solely on testing the component's interactions with the service without invoking the actual service logic.

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In which scenario is it NOT recommended to use ChangeDetectionStrategy.OnPush?

When a component has complex view logic with many nested components
When a component is stateful and has user interactions triggering updates
When a component relies on frequent data updates from external sources
When optimizing for performance is a top priority

ChangeDetectionStrategy.OnPush is not recommended when a component relies on frequent data updates from external sources because it can lead to manual triggering of change detection, reducing the benefits of this strategy. It's more suitable for components with infrequent updates or performance optimization.

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How can you ensure that a particular component is checked only once by Angular's change detection mechanism?

Using the ChangeDetectionStrategy.OnPush strategy.
Wrapping the component in an async pipe.
Manually triggering change detection for that component.
Adding the component to the AppModule declarations array.

You can ensure that a particular component is checked only once by Angular's change detection mechanism by using the ChangeDetectionStrategy.OnPush strategy. This strategy tells Angular to only run change detection on a component when its input properties change or when you manually trigger it. The other options do not provide a way to control change detection behavior in the same way.

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In what scenario might you need to use both ComponentFactoryResolver and ViewContainerRef together?

When creating a dynamic form with user-generated fields.
When applying CSS styles to a component.
When handling HTTP requests in Angular.
When using Angular animations in a component.

You might need to use both ComponentFactoryResolver and ViewContainerRef together when creating a dynamic form with user-generated fields. ComponentFactoryResolver is used to dynamically create components for each form field, and ViewContainerRef is used to manage the location where these components are inserted within the DOM. This combination allows you to dynamically generate and manage form fields based on user input or requirements. The other options do not typically require both ComponentFactoryResolver and ViewContainerRef together.

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