In which scenarios would you consider using the ChangeDetectionStrategy.OnPush for a component?
- When the component interacts with external APIs.
- When the component needs to re-render frequently.
- When the component relies on two-way data binding.
- When the component's data is immutable and only changes through input properties.
ChangeDetectionStrategy.OnPush is suitable when a component's data is immutable and only changes through input properties. This strategy optimizes performance by avoiding unnecessary change detection checks. It is not used when two-way data binding is required or when the component re-renders frequently. Interaction with external APIs is typically unrelated to the choice of change detection strategy.
How can you ensure that an Observable sequence completes after a certain number of emitted values?
- debounceTime
- distinctUntilChanged
- skip
- take
You can ensure that an Observable sequence completes after a certain number of emitted values by using the take operator. It allows you to specify how many emissions you want to take from the source Observable before it completes.
In NgRx, what would you use to handle side effects like API calls?
- Actions
- Effects
- Reducers
- Selectors
In NgRx, the "Effects" library is used to handle side effects like API calls. Effects are a way to interact with external sources such as APIs and perform asynchronous operations while maintaining the purity of reducers.
To achieve lazy loading in Angular, the loadChildren property uses the ________ syntax.
- Array
- Function
- Object
- String
To achieve lazy loading in Angular, you use the loadChildren property with a string that points to the module file to be loaded lazily. This string typically follows a specific syntax, where you specify the path to the module using a module import statement.
When content is projected into a child component, the data binding context remains that of the ________ component.
- Angular
- Child
- Host
- Parent
When content is projected into a child component, the data binding context remains that of the Parent component. This means that any data binding, variables, or properties you use in the projected content within the child component will be based on the data of the parent component that projected it. Understanding this is crucial for effective data communication in Angular.
Which of the following is a push-based mechanism in JavaScript?
- Callbacks
- Observables
- Promises
- Synchronous functions
Observables are a push-based mechanism in JavaScript. They allow you to work with asynchronous data streams, where data can be emitted at any time, rather than being pulled when needed as with Promises or using callbacks.
If you want to serve your Angular application on a specific port other than the default (4200), which command should you use?
- ng run --port 8080
- ng serve --default-port 8080
- ng serve --port 8080
- ng start --port 8080
To serve your Angular application on a specific port other than the default (4200), you should use the ng serve --port 8080 command. This command starts the development server on port 8080, allowing you to access your application using a different port.
How can you implement a custom validator that checks if a password and its confirmation are the same in a reactive form?
- Use the 'compare' method in Angular's built-in Validators.
- Create a custom validator function that compares the password and confirmation fields.
- Implement a directive for password confirmation validation.
- Utilize Angular's 'FormGroup' to compare the password and confirmation controls.
To implement a custom validator for password confirmation, you should create a custom validator function that compares the password and confirmation fields. This function should be added to the reactive form controls to ensure that the password and its confirmation are the same. Options 1, 3, and 4 are not the recommended approaches for this specific validation task.
In an e-commerce application, certain routes should only be accessible after a user logs in. To check the user's authentication status before allowing them to access these routes, which Route Guard would you use?
- CanActivate
- CanActivateChild
- CanLoad
- Resolve
The CanActivate route guard is used to protect routes based on whether a user is authenticated or not. It's commonly used to restrict access to routes that require user authentication.
In template-driven forms, which directive is used to conditionally apply CSS classes based on control validity?
- *ngFor directive.
- *ngIf directive.
- *ngTemplateOutlet directive.
- ngClass directive.
The ngClass directive is used in template-driven forms to conditionally apply CSS classes based on the control's validity state. You can use it to style form controls differently depending on whether they are valid, invalid, or untouched. The other directives listed serve different purposes and are not specifically designed for controlling CSS classes based on form control validity.