Angular Beginner Interview Questions
Prepare for your Angular interview with 30 beginner-level questions and answers covering components, modules, data binding, directives, services, and Angular CLI basics.
1. What is Angular?
Answer: Angular is a front-end framework developed and maintained by Google teams, used to build single-page applications (SPAs) with structured and scalable architecture.
2. What is TypeScript?
Answer: TypeScript is a superset of JavaScript that adds static types, classes, and interfaces to improve code safety and readability.
3. What is a Component?
Answer: A component is a basic UI unit in Angular that controls a part of the screen using:
- Template (HTML)
- Styles (CSS)
- TypeScript (Logic)
4. What is a Module?
Answer: In Angular, a Module (NgModule) is used to group related components, directives, pipes, and services into one functional block.
5. What is Data Binding?
Answer: In Angular, Data Binding is used to connect the component and view (HTML) so data stays synchronized.
Types of Data Binding (4 types):
- Interpolation: {{ data }} (component -> view)
- Property Binding: [property] (component -> element property)
- Event Binding: (event) (view -> component)
- Two-way Binding: [(ngModel)] (both ways sync)
6. What are Directives?
Answer: Directives are used to control and modify the DOM structure, appearance, or behavior of elements.
Types of Directives (3 types):
- Component Directives -> Every component itself is a directive
- Structural Directives -> change DOM structure *ngIf, *ngFor, *ngSwitch
- Attribute Directives -> change appearance/behavior ngClass, ngStyle
7. What is *ngIf?
Answer: In Angular, the *ngIf (now @if) is a structural directive used to add or remove elements based on a condition.
8. What is *ngFor?
Answer: In Angular, *ngFor (now @for) is a structural directive used to repeat elements for each item in a list.
9. What is a Service?
Answer: A service is a reusable class used to handle business logic and share data between components.
10. What is Dependency Injection?
Answer: Dependency Injection (DI) is a design pattern where Angular automatically provides required services to components instead of being created manually.
11. What is Routing?
Answer: In Angular, Routing is used to navigate between different views/components using a URL without reloading the page.
12. What is Angular CLI?
Answer: Angular CLI is a command-line tool used to create, build, test, and manage Angular applications.
13. What is a Template?
Answer: A template is the HTML structure of a component where Angular bindings and directives are used.
14. What is Interpolation?
Answer: In Angular, Interpolation ({{expressions}}) is used to display data from a component to a template.
15. What is Event Binding?
Answer: Event Binding (event) is used to handle user actions like clicks, input, and change events.
16. What is Property Binding?
Answer: Property Binding [property] is used to set DOM element properties using component data.
17. What are Pipes?
Answer: Pipes (symbol ‘|’) are used to transform data before displaying it in a template.
Example: date, uppercase, lowercase, titlecase, currency
18. What are Lifecycle Hooks?
Answer: Lifecycle hooks are methods that run at different stages of a component's life cycle.
Example: ngOnInit, ngOnDestroy, ngOnChanges, ngOnDestroy
19. What is Two-way Data Binding?
Answer: Two-way data binding [(ngModel)] is used to sync data both from the component to the view and from the view to the component.
20. What is SPA?
Answer: SPA (Single Page Application) is a web app that loads only one HTML page and dynamically updates content without a full reload.
21. What is HttpClient?
Answer: HttpClient is a built-in Angular service used to make HTTP requests like GET, POST, PUT, and DELETE to communicate with a backend API.
22. What is an Observable?
Answer: An Observable is a stream of data that can emit multiple values over time. Angular uses Observables (from RxJS) to handle async operations like HTTP calls.
23. What is RxJS?
Answer: RxJS (Reactive Extensions for JavaScript) is a library used in Angular to work with asynchronous data using Observables, operators, and streams.
24. What is a Guard?
Answer: A Guard is used to control access to routes in Angular. It checks conditions before allowing or blocking navigation to a specific page. Types of Guards:
- CanActivate: controls if a route can be accessed
- CanDeactivate: controls if a user can leave a route
- CanLoad: controls if a module can be loaded
25. What is Lazy Loading?
Answer: Lazy Loading is a technique in Angular where modules are loaded only when the user navigates to that route, instead of loading everything at once on startup.
26. What is a Decorator?
Answer: A Decorator is a special keyword used in Angular to attach metadata to a class, method, or property.
Examples:
- @Component: marks a class as a component
- @NgModule: marks a class as a module
- @Injectable: marks a class as a service
27. What is ngOnInit?
Answer: ngOnInit is a lifecycle hook method that runs once after the component is initialized. It is commonly used to fetch data or set up the component when it first loads.
28. What is FormGroup?
Answer: FormGroup is a class in Angular Reactive Forms used to group multiple form controls together and manage the entire form as one unit.
29. What is the difference between Template-driven and Reactive Forms?
Answer: Both are ways to handle forms in Angular.
- Template-driven Forms: logic is written in HTML, simple and easy for small forms
- Reactive Forms: logic is written in TypeScript, with more control and better suited for complex forms
30. What is ViewChild?
Answer: ViewChild is a decorator used to access a child component, directive, or DOM element directly from the parent component's TypeScript class.