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.
Which directive in Angular is used to loop over an array and render a list?
- *ngClass
- *ngFor
- *ngIf
- *ngSwitch
In Angular, the *ngFor directive is used to loop over an array and render a list. It iterates through the elements of an array or a collection and generates HTML elements for each item in the array. This is commonly used for rendering dynamic lists, such as a list of items retrieved from an API. *ngIf is used for conditional rendering, *ngSwitch is used for switching between multiple views, and *ngClass is used for dynamically adding or removing CSS classes.
You're building a tabbed interface where only one tab content is displayed at a time, and others are conditionally hidden. Which built-in directive would be most useful to achieve this?
- ngFor Directive
- ngIf Directive
- ngShow Directive
- ngSwitch Directive
To create a tabbed interface where only one tab content is displayed at a time and others are conditionally hidden, the ngIf directive would be most useful. ngIf is a structural directive that conditionally adds or removes elements from the DOM based on a condition. You can use it to conditionally render the content of the selected tab while hiding others.
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.
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.