How does the ChangeDetectionStrategy.OnPush improve performance in Angular components?
- It enables two-way data binding
- It forces constant change detection
- It prevents data mutation
- It reduces the frequency of change detection cycles
The ChangeDetectionStrategy.OnPush setting in Angular tells the framework to perform change detection only when the inputs to a component change, rather than after every event. This optimization reduces the frequency of change detection cycles, which can significantly improve performance, especially in complex applications.
Which Angular CLI command helps in updating your Angular application to the latest version?
- ng migrate
- ng refresh
- ng update
- ng upgrade
The ng update command in Angular CLI is used to update your Angular application to the latest version of Angular and its dependencies. It helps you keep your application up-to-date with the latest features, bug fixes, and security patches.
Which of the following is the primary building block of an Angular application?
- Component
- Directive
- Module
- Service
In Angular, a component controls a patch of the screen called a view. Components are the main way to build and specify elements and logic on the page, making them the primary building block of an Angular application.
How can you set default values for form controls in a template-driven form?
- Use the defaultValue attribute.
- Assign values directly in the template.
- Set values programmatically in the component.
- Use the ngDefaultControl directive.
In template-driven forms, default values for form controls are typically set programmatically in the component by initializing the corresponding form control variables with the desired default values. While you can assign values directly in the template, this doesn't allow for dynamic default values or interaction with the component logic. The other options mentioned are not common practices for setting default values in template-driven forms.
What does the map operator in RxJS primarily do?
- Combines multiple Observables
- Filters data emitted by an Observable
- Subscribes to an Observable
- Transforms data emitted by an Observable
The map operator in RxJS primarily transforms data emitted by an Observable. It allows you to apply a function to each item emitted by the source Observable and returns a new Observable with the transformed values.
You are working on a large application where you need to display complex modal dialogs based on user interactions. How can dynamic components assist in this scenario?
- Dynamic components allow you to add styling to elements.
- Dynamic components can only be used in AngularJS.
- Dynamic components enable lazy loading of modules.
- Dynamic components can be created and rendered at runtime.
Dynamic components in Angular allow you to create and render components at runtime. This is particularly useful for displaying complex modal dialogs based on user interactions. You can dynamically load the modal component when needed, keeping the main application bundle smaller and improving performance. The other options do not accurately describe the capabilities of dynamic components.
What potential issue can arise when using Lazy Loading without properly planning the module structure?
- Circular dependencies
- Decreased maintainability
- Difficulty in routing configuration
- Increased initial loading time
When using Lazy Loading without proper planning, circular dependencies can arise. This occurs when two or more modules depend on each other, causing issues with module resolution and potentially leading to runtime errors. It's essential to structure modules carefully to avoid this problem.
Which method would you use in HttpInterceptor to catch and handle HTTP errors?
- catchError
- handleError
- handleError and catchError
- intercept
In an HttpInterceptor, you would use the intercept method to catch and handle HTTP errors. This method intercepts outgoing HTTP requests and incoming responses, giving you the opportunity to handle errors and modify requests before they are sent.
How can you analyze the bundle size of your Angular application?
- Using the "ng analyze" command
- Checking the browser console
- Using "npm start"
- Examining package.json
To analyze the bundle size of your Angular application, you can use the "ng analyze" command. This command provides detailed information about the size of each module and dependency in your application, helping you identify and optimize large bundles.
To make a service available only within a specific module, set the providedIn property to the ________ of that module.
- 'providers'
- 'imports'
- 'declarations'
- 'exports'
To limit the availability of a service to a specific module in Angular, you should set the 'providedIn' property to 'providers' of that module. This ensures that the service is scoped to the module where it's provided and can't be accessed outside of it. The other options ('imports,' 'declarations,' and 'exports') are unrelated to specifying service scope and purpose.