When you want to get only the first emitted value from an Observable and then complete, you should use the ________ operator.
- debounceTime
- mergeMap
- skip
- take
The take operator in RxJS is used to receive only the first 'n' values emitted by an Observable and then automatically complete the Observable. It's useful when you're interested in a limited initial set of data.
In template-driven forms, which directive is utilized to implement a group of form controls?
- ngControlGroup
- formControlGroup
- ngFormGroup
- formGroup
In template-driven forms, the formGroup directive is used to implement a group of form controls. It allows you to group related form controls together, making it easier to manage their validation and state. The other options mentioned are not valid directives for implementing form control groups in template-driven forms.
Which Angular feature allows you to project different parts of content into multiple predefined slots inside a child component?
- ng-content
- ng-projection
- ng-slot
- ng-template
In Angular, the feature that allows you to project different parts of content into multiple predefined slots inside a child component is the directive. It enables you to define multiple tags with select attributes in the child component's template, and then, in the parent component, specify which content goes into each slot using the select attribute's value. The other options are not valid Angular directives or features for content projection.
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.
You notice that a particular component in your application re-renders too often, causing performance issues. What steps can you take to optimize it?
- Implement shouldComponentUpdate()
- Increase the component's complexity
- Use more inline styles
- Ignore the issue and focus on other components
To optimize a component that re-renders too often and causes performance issues in a React application, you can implement the shouldComponentUpdate() lifecycle method. This allows you to control when the component should update and re-render, potentially improving performance. The other options are not effective ways to address this issue.
Imagine you have a modal component, and you want users to define custom header, body, and footer for each modal instance. How would you set up the modal component to achieve this?
- Use Angular Templates for Header, Body, and Footer
- Use ng-container for Header, Body, and Footer
- Use Angular Dynamic Components for Header, Body, and Footer
- Use ng-template for Header, Body, and Footer
To allow users to define custom header, body, and footer for each modal instance in Angular, you should use Angular Dynamic Components. This approach allows users to create and insert components dynamically at runtime, making it suitable for the scenario where custom content needs to be defined for each modal instance. While other options like templates, ng-container, and ng-template can be used for various purposes, they don't provide the same level of flexibility as dynamic components in this context.
How can you project content from a parent component into a child component's template?
- Using structural directives like *ngFor.
- Using input properties.
- Using the ViewChild decorator.
- Using Angular modules.
You can project content from a parent component into a child component's template using structural directives like *ngFor, *ngIf, etc. These directives allow you to conditionally render or iterate over content in the child component's template based on data passed from the parent. Input properties are used to pass data, but they don't project content in this way. The other options are not related to content projection.
You are tasked with implementing a feature where, upon clicking a button, the user should be redirected to the home page. Which method or feature of Angular's router would you utilize?
- router.navigate(['/home']);
- router.navigate(['home']);
- router.navigateByUrl('/home');
- router.to(['/home']);
To redirect the user to the home page using Angular's router, you should use the router.navigate(['/home']); method. This method navigates to the specified route, in this case, '/home', which represents the home page. The other options are either incorrect or do not exist in Angular's routing syntax.
How can you achieve nested routing (child routes) within an Angular application?
- By defining child routes in the RouterModule
- By using Angular's loadChildren feature
- By using Angular's canActivateChild guard
- By applying a deep route nesting hierarchy
To achieve nested routing (child routes) in Angular, you define child routes within the RouterModule configuration. This allows you to create a hierarchical structure of routes. The other options relate to Angular's routing features but do not specifically address the process of achieving nested routes.