Custom validators in Angular are functions that return an object of type ____ when the validation fails.
- FormControl
- ValidationErrors
- number
- string
Custom validators in Angular are functions that return an object of type ValidationErrors when the validation fails. The ValidationErrors object holds information about the validation error and can be used to display error messages.
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).
What would you test in a custom pipe that formats and displays dates?
- Pipe's NgModule
- Pipe's constructor
- Pipe's template
- Pipe's transform method
In a custom date formatting pipe, you should test the Pipe's transform method to ensure it formats and displays dates correctly.
You are testing a custom pipe that transforms user input into a URL-friendly format. What edge cases should you consider in your tests?
- Empty input
- Invalid URL characters
- Long input
- Special characters
When testing the custom pipe, you should consider special characters as an edge case. Special characters may need proper transformation, and testing how the pipe handles them is important.
Which Router Event can be used to perform actions after a navigation has successfully completed?
- NavigationCancel
- NavigationEnd
- NavigationError
- NavigationStart
To perform actions after a navigation has successfully completed, you can use the NavigationEnd event from the Router events.
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.