Angular Senior Interview Essentials: Easy-Level Quiz Quiz

Explore core Angular interview concepts with these essential, easy-level questions designed for developers aiming for senior roles. This quiz highlights fundamental Angular principles, best practices, and potential pitfalls encountered in real-world applications.

1. Understanding Angular Lifecycle Hooks

   Which lifecycle hook is most appropriate for initializing data that depends on component inputs in an Angular component?

   1. ngAfterContentInit
   2. ngDoCheck
   3. ngOnInit
   4. ngOnChanges

   Explanation: The ngOnInit lifecycle hook is designed for component initialization after its inputs are set, making it ideal for setting up data that relies on those inputs. ngAfterContentInit occurs after projecting content into the component, which does not guarantee all input properties are in place. ngOnChanges fires on every change of input properties, but it's meant for responding to those changes, not for initializing dependent data. ngDoCheck is used for custom change detection, not typically for initialization.

2. Angular Dependency Injection Providers

   In Angular, how can you make a service available only to a single component and its child components, rather than the entire application?

   1. Add the service to the app module’s imports
   2. Set providedIn: 'root' in the service decorator
   3. Provide the service in the component’s providers array
   4. Register the service in the main.ts file

   Explanation: By listing the service in a component’s providers array, a new instance is created specifically for that component and its descendants, limiting its scope. Adding the service to the app module’s imports has no effect on service instance creation. Using providedIn: 'root' makes the service a singleton available throughout the application. The main.ts file is not used for registering dependency injection providers.

3. Structural Directives vs. Attribute Directives

   Which statement best differentiates structural directives from attribute directives in Angular?

   1. Structural directives are used for data binding, whereas attribute directives are used for event handling.
   2. Attribute directives must be prefixed with an asterisk, while structural directives do not require any prefix.
   3. Structural directives alter the layout by adding or removing elements in the DOM, while attribute directives only change the behavior or appearance of existing elements.
   4. Attribute directives can create new HTML tags, while structural directives cannot.

   Explanation: Structural directives (such as *ngIf and *ngFor) change the DOM layout by adding or removing elements dynamically, whereas attribute directives modify the appearance or behavior of existing DOM elements. Attribute directives cannot create new HTML tags, and structural directives are not specifically for data binding. The asterisk prefix is unique to structural directives, not attribute ones.

4. Angular Reactive Forms Basics

   If you want to create a form group dynamically in Angular and track the validity of its controls, which feature should you use?

   1. FormArray
   2. Template-driven forms
   3. Reactive Forms
   4. AsyncValidator

   Explanation: Reactive Forms provide a model-driven approach for building forms dynamically and tracking state and validations programmatically. Template-driven forms rely more on directives and don't offer as much dynamic control. FormArray is used within reactive forms to manage arrays of controls, not to create form groups themselves. AsyncValidator is a validation mechanism, not a form structure feature.

5. Change Detection Strategy

   Which Angular change detection strategy reduces the number of checks by only updating the component when its inputs change or an event is triggered within its view?

   1. Manual
   2. OnPush
   3. Automatic
   4. Default

   Explanation: The OnPush change detection strategy optimizes performance by only running change detection for a component when its input properties change or an event is fired within its template. The Default strategy checks the entire component tree on every change detection cycle. There are no built-in strategies named Manual or Automatic; those options are distractors.