Angular Interview Questions and Answers: Your Ultimate Guide

Angular is a popular framework for building dynamic, modern web applications. As demand for skilled Angular developers increases, interviews for such roles become more competitive. To help you prepare, we’ve compiled a list of common Angular interview questions and their answers.

1. What is Angular?

Answer: Angular is a TypeScript-based open-source web application framework developed by Google. It helps developers create scalable, maintainable, and modular applications by offering features like two-way data binding, dependency injection, and component-based architecture.

Follow-Up:

Why choose Angular over other frameworks like React or Vue?

Answer:

Angular offers a full-fledged solution with everything a developer needs right out of the box. It supports routing, forms, HTTP client, and much more, which eliminates the need for external libraries, unlike React or Vue.

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2. What are Angular Modules?

Answer: Angular modules, or NgModules, are containers for a cohesive block of code dedicated to a specific domain, workflow, or closely related set of capabilities. An Angular application is built using at least one module called the AppModule.

Follow-Up:

Can you explain the role of AppModule in an Angular application?

Answer:

AppModule is the root module of the application. It bootstraps the application by defining the components, directives, and services that make up the app.

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3. Explain Dependency Injection in Angular.

Answer:

Dependency Injection (DI) is a design pattern used in Angular to create and inject dependencies into components and services. It allows for loose coupling and increased flexibility. For example, if a component needs a service to perform a task, Angular’s DI system can provide the instance of that service when the component is initialized.

Follow-Up:

How does Angular know where to inject dependencies?

Answer:

Angular uses metadata provided by decorators like @Injectable to define which dependencies to inject into classes.

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4. What is Data Binding in Angular?

Answer:

Data binding is the process of synchronizing the data between the model (business logic) and the view (user interface) components. Angular supports four types of data binding:

• Interpolation: For binding data from the component to the view using curly braces {{}}.

• Property Binding: For binding component properties to elements.

• Event Binding: For handling events like clicks or key presses.

• Two-way Data Binding: For binding both to the model and the view, typically using ngModel.

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5. What are Angular Components?

Answer:

Components are the basic building blocks of an Angular application. A component controls a portion of the view (HTML) and contains both the logic (TypeScript) and the template (HTML) for displaying data.

Follow-Up:

What are decorators, and how are they used in Angular components?

Answer:

Decorators are special functions that modify the behavior of a class, method, or property in Angular. The @Component decorator is used to define metadata for a component, such as its selector, template, and styles.

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6. Explain the Angular Lifecycle Hooks.

Answer:

Angular components go through a series of events from their creation to destruction. These are known as lifecycle hooks:

• ngOnInit: Called once the component is initialized.

• ngDoCheck: Called during every change detection run.

• ngOnChanges: Called whenever input properties change.

• ngOnDestroy: Called right before the component is destroyed.

Each lifecycle hook allows developers to hook into key moments in the component’s lifecycle.

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7. What are Angular Directives?

Answer:

Angular directives are used to extend the behavior of DOM elements. There are three types:

• Component Directives: Create custom HTML tags using @Component.

• Structural Directives: Alter the DOM structure, like *ngIf or *ngFor.

• Attribute Directives: Change the appearance or behavior of elements, like ngClass and ngStyle.

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8. How do you handle forms in Angular?

Answer:

Angular provides two ways to handle forms:

• Template-driven forms: Relies on directives like ngModel for two-way data binding.

• Reactive forms: More powerful and gives control over form validation and values using FormControl and FormGroup.

Follow-Up:

What is the main difference between template-driven and reactive forms?

Answer:

Template-driven forms are simple to use and rely heavily on the template, while reactive forms are more scalable and provide more explicit control, suitable for complex use cases.

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9. What is Routing in Angular?

Answer:

Routing in Angular enables developers to navigate between different views or components. The Angular Router maps URLs to components and allows navigation using RouterLink and RouterOutlet.

Follow-Up:

What is lazy loading, and how does it work in Angular routing?

Answer:

Lazy loading allows you to load feature modules on demand, reducing the initial load time of the application. You can configure lazy loading using the loadChildren property in the Routes array.

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10. How does Change Detection work in Angular?

Answer:

Angular’s change detection system is responsible for keeping the view in sync with the model. Angular uses the zone.js library to detect changes in asynchronous tasks (like HTTP requests) and automatically updates the DOM when a change occurs.

Follow-Up:

What is OnPush change detection strategy?

Answer:

OnPush is a more efficient change detection strategy that checks for changes only when the input properties change, offering better performance for components that deal with a large amount of data.

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Conclusion

These questions cover a wide range of topics from Angular’s core architecture to its advanced features like routing and change detection. Preparing these answers will give you a solid foundation for Angular interviews, ensuring you can confidently explain key concepts and demonstrate practical knowledge. Keep practicing and exploring Angular’s documentation to stay updated with the latest features and best practices!