What is the purpose of the ngOnChanges lifecycle hook?
- Detect changes in input data
- Perform HTTP requests asynchronously
- Render the component to the DOM
- Determine the component's constructor name
The ngOnChanges lifecycle hook in Angular is primarily used to detect changes in input data bound to a component. It is triggered whenever input properties of the component change. This hook is valuable for responding to changes in input data and taking appropriate actions based on those changes. The other options are not the primary purpose of this hook.
The operator that's used to handle errors in an Observable sequence is ________.
- catchError
- filter
- map
- subscribe
The catchError operator in RxJS is used to handle errors that occur in an Observable sequence. It allows you to gracefully handle errors and continue the sequence or provide fallback behavior.
Lazy loading in Angular allows you to load feature modules on-demand using the ________ property in the route configuration.
- asyncLoad
- lazyLoad
- loadChildren
- loadModule
The blank should be filled with "loadChildren." In Angular, lazy loading is achieved by using the loadChildren property in the route configuration. This property specifies the path to the module that should be loaded lazily when the associated route is activated, improving application performance.
Your team wants to maintain consistent code style and practices across Angular projects. Which Angular CLI feature would you use to enforce this?
- TSLint
- ESLint
- StyleLint
- Codelyzer
To maintain consistent code style and practices in Angular projects, you would use ESLint. ESLint is a widely-used linting tool that provides extensive configuration options and can enforce coding standards and best practices for TypeScript and JavaScript code, making it a suitable choice for maintaining consistency.
For handling offline data synchronization in an Angular app, which RxJS operator would be most appropriate?
- catchError
- mergeMap
- publishReplay
- retry
To handle offline data synchronization in an Angular app, the publishReplay operator can be most appropriate. This operator allows you to cache and replay emitted values, making it useful for scenarios where you want to store and replay network requests or data updates when the device is offline and then sync them when it's online.
How would you retrieve query parameters from the current route in an Angular application?
- Using the ActivatedRoute service's queryParams property.
- By accessing the router state's queryParameters property.
- Through the RouterLinkActive directive.
- By subscribing to the router's queryParams observable.
To retrieve query parameters from the current route in an Angular application, you would typically use the ActivatedRoute service's queryParams property. This property provides access to the parsed query parameters, allowing you to read and utilize them within your component. The other options are not the standard way to access query parameters in Angular. The RouterLinkActive directive is used for styling active links, not for parameter retrieval.
What's the benefit of using immutable data structures in Angular applications?
- They allow for more efficient data binding.
- They can be easily modified in-place.
- They simplify the component creation process.
- They enhance code readability.
Using immutable data structures in Angular provides benefits like more efficient data binding. Immutable data structures prevent unexpected changes to the data, making it easier to track changes in the application state. They also help optimize change detection, leading to better performance. While the other options may have their merits, they do not directly address the benefits of immutability in Angular.
In template-driven forms, how can you access the overall form status?
- Accessing the formStatus variable
- By calling the this.formStatus() method
- Using the ngForm directive
- Utilizing the form property in a template
In template-driven forms, you can access the overall form status by utilizing the 'form' property in a template. This 'form' property provides information about the form's status, such as whether it's valid, invalid, or pristine. It's a built-in feature for managing and validating forms in Angular.
To capture changes in the @Input() property, one should implement the ______ interface.
- AfterViewInit
- OnChanges
- OnDestroy
- OnInit
To capture changes in the @Input() property, one should implement the OnChanges interface. The OnChanges lifecycle hook provides a method, ngOnChanges, which is called whenever any of the input properties of a component change. This allows you to react to input changes.
For optimizing performance in large lists where data is immutable, one should use the ChangeDetectionStrategy.______ strategy.
- Default
- OnPush
- Always
- Manual
To optimize performance in Angular applications, especially when dealing with large lists and immutable data, you should use the ChangeDetectionStrategy.OnPush strategy. This strategy minimizes change detection cycles by only checking components when their inputs change. It can significantly improve performance. The other options are not valid strategies for optimizing change detection.