In an Angular application, how can you optimize a component to be checked only once by Angular's change detection mechanism?
- Use the Default change detection strategy
- Use the EventEmitter to trigger change detection
- Use the OnPush change detection strategy
- Use the Renderer2 to skip change detection
To optimize a component to be checked only once by Angular's change detection, you should use the OnPush change detection strategy. This strategy reduces unnecessary checks.
You're building a type-ahead search feature in an Angular application. The user input should trigger API calls, but you want to avoid making unnecessary calls for every keystroke. Which RxJS operators can help optimize this?
- filter and reduce
- mergeMap and throttleTime
- switchMap and debounceTime
- take and pluck
To optimize the type-ahead search feature, you can use switchMap to cancel previous API calls and only return the latest result, and debounceTime to delay the API call until the user stops typing, avoiding unnecessary calls for every keystroke.
What language is used to write E2E tests in Protractor?
- Java
- JavaScript
- Python
- TypeScript
JavaScript is the language used to write E2E tests in Protractor, making it compatible with Angular applications, as Angular also uses JavaScript.
What is the significance of the async and fakeAsync utilities in Angular testing?
- async is used for asynchronous unit tests
- async is used for promise-based asynchronous tests
- fakeAsync is used for simulating asynchronous operations
- fakeAsync is used for synchronous unit tests
In Angular testing, the **async** utility is used to handle promise-based asynchronous tests, while the **fakeAsync** utility is used for simulating asynchronous operations in a synchronous manner. These utilities help control and test asynchronous behavior effectively in different testing scenarios.
How would you implement cross-field validation in a reactive form?
- Create a new form module
- Define custom validators
- Use the FormArray class
- Utilize Angular templates
To implement cross-field validation in a reactive form, you would typically define custom validators that check and enforce validation rules involving multiple fields.
Which feature in Angular allows you to create custom HTML elements that can be used outside Angular applications?
- Angular Components
- Angular Elements
- Angular Modules
- Angular Services
The feature in Angular that allows you to create custom HTML elements usable outside Angular applications is Angular Elements.
Which Angular CLI command is used to generate a new component?
- ng create component
- ng generate component
- ng make component
- ng new component
To generate a new component in Angular using the CLI, you use the ng generate component command.
What is the significance of the declarations array in an Angular module?
- To configure route paths
- To declare components in the module
- To define component dependencies
- To set up HTTP interceptors
The declarations array in an Angular module is used to declare components that are part of the module. This is important for Angular to know which components are available within the module.
In Angular, the _____ pipe is used to automatically subscribe and unsubscribe from an Observable.
- async
- map
- reduce
- switchMap
In Angular, the async pipe is used to automatically subscribe and unsubscribe from an Observable. It simplifies the management of Observable subscriptions in templates, ensuring proper cleanup.
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.