You're working on an application that has several feature modules. To improve the user experience, you decide to preload some modules in the background while the user is interacting with the app. How can you implement this behavior?
- Manually load modules using import() as the user interacts with different parts of the app
- Use localStorage to cache module data and preload them when the app loads
- Use the Angular Router Preloading Strategy to preload specific modules
- Utilize a service worker to cache and preload modules as a background process
To improve the user experience by preloading specific modules in the background as the user interacts with the app, you can use the Angular Router Preloading Strategy. It allows you to preload modules when needed, optimizing the app's performance.
You are building a form where certain fields need to be shown or hidden based on the selection of a dropdown. How can you dynamically add or remove validations on these fields based on their visibility?
- Create separate forms for each combination of visible fields.
- Use ngClass to toggle validations dynamically.
- Use ngSwitch to toggle validations based on the dropdown value.
- Use the ngIf directive to conditionally add or remove validators.
To dynamically add or remove validations on fields based on their visibility in an Angular form, you should use the ngIf directive to conditionally add or remove validators. This approach allows for dynamic validation based on UI interactions.
In template-driven forms, the _____ directive is used to create two-way data bindings on an input field.
- *ngFor
- *ngIf
- *ngModel
- *ngSwitch
In template-driven forms, the *ngModel directive is used to create two-way data bindings on an input field, allowing the field to sync its value with a component property.
When testing an Angular service, why might you use a spy?
- To create a new instance of the service
- To mock dependencies used by the service
- To secretly record user interactions
- To simulate service method calls
In Angular testing, you use a spy to mock dependencies used by the service being tested, allowing you to control and observe interactions with those dependencies.
In what scenario would you create a custom directive instead of using a component in Angular?
- Handling user input
- Implementing complex logic
- Managing application state
- Reusing UI behavior
You would create a custom directive in Angular when you want to reuse UI behavior across different parts of your application.
Which RxJS operator would you use to combine multiple Observables into a single Observable?
- combineLatest()
- concatMap()
- reduce()
- switchMap()
To combine multiple Observables into a single Observable, you can use the combineLatest() operator, which emits a new value when any of the source Observables emits a new value.
To validate that at least one control within a Form Array has a specific value, you would use a _______ validator.
- Array
- Custom
- MinLength
- Required
To validate that at least one control within a Form Array has a specific value, you would use a Custom validator. A custom validator allows you to define your own validation logic.
How can you display validation error messages for a custom validator in Angular?
- Use Reactive Forms
- Use a FormBuilder
- Use a FormGroup
- Use a Validation Message
To display validation error messages for a custom validator in Angular, you can use a Validation Message. This involves creating custom error messages and binding them to the form control to inform users of validation issues.
When using Angular Elements, what considerations must be taken into account for handling data and events in the custom element?
- Avoiding data sharing between components
- Direct DOM manipulation
- Ensuring data encapsulation and event emitters
- Use Angular services for data communication
When working with Angular Elements, it's important to use Angular services for data communication to ensure proper encapsulation and handling of data and events.
How can you apply a custom validator to a form control in Angular?
- Applying ngFor directive
- By extending the FormControl class
- Using the async pipe
- Using the ngIf directive
You can apply a custom validator to a form control in Angular by extending the FormControl class and implementing your validation logic within it.