What is the purpose of the ControlValueAccessor interface in Angular forms?
- It is used to access form control values in JavaScript code.
- It enables custom form controls to work with Angular's reactive forms.
- It provides a way to access the values of a FormGroup.
- It allows you to control the layout of form elements in Angular templates.
The ControlValueAccessor interface in Angular forms is used to enable custom form controls to work seamlessly with Angular's reactive forms. It acts as a bridge between the custom form control and Angular's form infrastructure, allowing the control to interact with form directives, template-driven forms, and reactive forms. Options 1, 3, and 4 do not accurately describe the purpose of ControlValueAccessor.
What is the primary benefit of using lazy loading in Angular applications?
- Better performance in data binding
- Enhanced security
- Faster initial loading
- Improved SEO
The primary benefit of using lazy loading in Angular applications is faster initial loading. Lazy loading allows you to load only the necessary modules and components when they are needed, reducing the initial bundle size and improving the application's loading speed.
You're building a dashboard that fetches and displays data from multiple API endpoints simultaneously. To ensure that all data is loaded before rendering the dashboard, which RxJS technique would you employ?
- combineLatest
- forkJoin
- merge
- zip
To ensure that all data from multiple API endpoints is loaded before rendering the dashboard, you should use the forkJoin operator in RxJS. It combines the results of multiple observables and emits only when all observables complete.
How can you pass data to a dynamically created component?
- Using Angular's data binding with @Input().
- By directly modifying the component's internal state.
- Through a centralized data store like Redux.
- By using Angular services and injecting data.
To pass data to a dynamically created component in Angular, you can use Angular's data binding with @Input() decorators. This allows you to bind properties of the dynamic component to the parent component's properties, enabling seamless data communication between them. The other options may be possible in certain scenarios but are not the standard approach for passing data to dynamically created components.
Your application requires a custom directive that modifies the structure of the DOM based on user roles. Which type of directive should you consider creating?
- Attribute Directive
- Component Directive
- Service Directive
- Structural Directive
When you need to modify the structure of the DOM based on user roles, a Structural Directive is the most appropriate choice. Structural Directives, such as ngIf and ngFor, can conditionally add or remove elements from the DOM, allowing you to customize the view based on user roles or conditions. This flexibility makes them well-suited for this scenario.
An Observable that can emit multiple values over time is different from a Promise, which can resolve only ________.
- multiple times
- never
- once
- twice
An Observable can emit multiple values over time, whereas a Promise can resolve only once. This fundamental difference makes Observables suitable for handling asynchronous streams of data, while Promises are used for handling single asynchronous operations.
Which decorator is used to inject a service into an Angular component?
- @Injectable()
- @Component()
- @Service()
- @InjectService()
To inject a service into an Angular component, you use the @Injectable() decorator. This decorator is applied to the service class, allowing Angular's dependency injection system to recognize and provide the service when requested by a component. The other options (@Component(), @Service(), @InjectService()) are not used for this purpose.
When using the OnPush strategy, a component will be checked if a new object reference is passed to one of its ________.
- Inputs
- Methods
- Outputs
- Variables
When using the OnPush change detection strategy in Angular, a component will be checked if a new object reference is passed to one of its inputs. This means that the component will only re-render if there's a change in the input values. The OnPush strategy is an optimization to reduce unnecessary checks and re-renders.
Change detection in Angular can be optimized by ensuring data structures are ________.
- Encapsulated
- Immutable
- Mutable
- Private
Change detection in Angular can be optimized by ensuring data structures are immutable. Immutable data structures ensure that when changes are made to data, a new reference is created, which helps Angular's change detection mechanism identify changes efficiently. By contrast, mutable data structures may not trigger change detection as expected.
You're building a chat application where messages should be displayed in real-time. However, if the user is not on the chat page, the messages should be buffered and displayed all at once when the user returns. Which RxJS operator or concept would help achieve this?
- BehaviorSubject
- BufferTime
- DebounceTime
- SwitchMap
To achieve real-time message display with buffering when the user returns, you can use the RxJS bufferTime operator. bufferTime collects items emitted within a specified time window and then emits the collected items as an array. This allows you to buffer messages and display them together when appropriate.