How can you ensure that an Observable completes and releases resources after emitting a certain number of values?
- Use the complete method
- Use the finalize operator
- Use the takeUntil operator
- Use the unsubscribe method
To ensure an Observable completes and releases resources after emitting a certain number of values, you can use the takeUntil operator to specify a condition for completion.
What is the difference between dirty and touched properties of a form control?
- Dirty indicates interaction, touched indicates modification.
- Dirty indicates it's required, touched indicates it's optional.
- Dirty indicates modification, touched indicates interaction.
- Dirty indicates optional, touched indicates required.
In Angular, the dirty property indicates that a form control has been modified, while the touched property indicates that a form control has been interacted with (e.g., focused or blurred).
In RxJS, which operator can be used to catch and handle errors in an Observable stream?
- catchError
- combineLatest
- filter
- map
In RxJS, the catchError operator is used to catch and handle errors in an Observable stream, allowing for graceful error handling.
What would be a common use case for using a 'canDeactivate' Route Guard in an Angular application?
- Checking if a user is authenticated before routing to a protected route
- Confirming navigation changes before leaving a form or editing page
- Preventing multiple components from loading in the same router-outlet
- Resolving data asynchronously before activating a route
A common use case for the 'canDeactivate' Route Guard is to confirm navigation changes before leaving a form or editing page. It provides a user confirmation dialog.
Which testing tool is commonly used for performing E2E tests in Angular applications?
- Jasmine
- Karma
- Mocha
- Protractor
Protractor is a widely used testing tool for performing End-to-End (E2E) tests in Angular applications. It is specifically designed for testing Angular apps.
You need to build a form that fetches and populates its options (e.g., a dropdown list) from an API. Which form approach would allow you more flexibility and control over handling data asynchronously?
- Template-driven forms
- Reactive forms
- Both provide the same flexibility
- None of the above
To handle data asynchronously and fetch options from an API, Reactive forms would be the better choice as they offer more flexibility and control over handling asynchronous data.
You're experiencing a situation where your Angular application works as expected during development but breaks when running unit tests. What steps can you take to identify and rectify the discrepancy?
- Analyze environment differences
- Check for asynchronous code
- Debug the failing unit tests
- Increase unit test coverage
To identify and rectify the discrepancy between development and unit tests, you should analyze environment differences that might be affecting the tests.
In Angular, developers can use the _____ service to log errors to the console during debugging.
- Console
- Error
- Http
- Log
In Angular, developers can use the Error service to log errors to the console during debugging, making it easier to diagnose issues.
To asynchronously validate a form control value, you can use a _____ validator.
- asyncValidator
- mergeMap
- subscribe
- syncValidator
To asynchronously validate a form control value in Angular, you can use an asyncValidator.
The process of initializing data properties of a component just before it's displayed is done in the _____ lifecycle hook.
- ngAfterViewInit
- ngInit
- ngOnChanges
- ngOnInit
The process of initializing data properties of a component just before it's displayed is done in the ngOnInit lifecycle hook.