Top 10 Angular Developer Interview Questions & Answers in 2024

1. How does change detection work in Angular, and what are the different strategies for optimizing change detection performance?

Angular uses change detection to track and update the DOM when the application state changes. Strategies for optimizing change detection include:

• OnPush Change Detection: Sets change detection to occur only when the component's input properties change or when explicitly triggered.
• Immutable Data Structures: Use immutable objects to ensure that object references change when the data changes.
• Async Pipe: Utilize the async pipe for handling asynchronous operations, ensuring efficient change detection.

2. Explain Angular Dependency Injection and its role in creating modular and maintainable applications.

Angular Dependency Injection (DI) is a design pattern used to manage the creation and injection of dependencies in a modular and maintainable way. It allows components, services, and other objects to depend on abstractions rather than concrete implementations, facilitating easier testing, reusability, and maintainability of code. DI is essential for creating loosely coupled and highly modular Angular applications.

3. How can you achieve cross-component communication in Angular, and what scenarios are suitable for different communication techniques?

Cross-component communication in Angular can be achieved using techniques such as:

• @Input and @Output: For parent-child component communication.
• ViewChild and ContentChild: For accessing child components and elements.
• Services: For sharing data and functionality between components, especially when components are not directly related.

Choose the appropriate technique based on the relationship and requirements of the communicating components.

4. Discuss the role of Angular Forms and template-driven forms versus reactive forms. When would you choose one over the other?

Angular Forms provide a way to handle user input and validation. Template-driven forms rely on directives within the template, while reactive forms use a more explicit, model-driven approach using TypeScript. Use template-driven forms for simpler scenarios and when form logic is closely tied to the component's template. Reactive forms are preferred for complex forms, dynamic form creation, and enhanced testability.

5. How does lazy loading work in Angular, and what benefits does it offer for large-scale applications?

Lazy loading in Angular involves loading modules only when they are required, reducing the initial bundle size and improving application loading times. It is particularly beneficial for large-scale applications where minimizing the initial payload is critical. Lazy loading is achieved by configuring routes with the loadChildren property, ensuring that modules are loaded on demand.

6. Explain the concept of Angular Interceptors and provide examples of how they can be used to intercept HTTP requests and responses.

Angular Interceptors allow you to intercept HTTP requests and responses globally. Examples of interceptor use cases include adding authentication headers, logging, or modifying request/response data. Interceptors are implemented by creating a service that implements the HttpInterceptor interface and registering it in the app's providers.

7. How can you optimize Angular application performance, and what tools can assist in identifying performance bottlenecks?

Optimizing Angular performance involves techniques such as Ahead-of-Time (AOT) compilation, lazy loading, and tree shaking to minimize the bundle size. Tools like Angular CLI, Chrome Developer Tools, and Augury can assist in profiling and identifying performance bottlenecks. Profiling the application, analyzing the change detection cycle, and optimizing the rendering process contribute to better performance.

8. Discuss Angular Pipes and their role in transforming data in templates. Provide examples of built-in pipes and scenarios where custom pipes might be necessary.

Angular Pipes are used to transform and format data in templates. Built-in pipes include DatePipe, UpperCasePipe, and CurrencyPipe. Custom pipes are created when specific transformations are needed. For example, a custom pipe might be created to filter or format a custom data type or to implement a unique transformation logic not covered by built-in pipes.

9. How does Angular Routing work, and what are the advantages of using Angular Router Guards?

Angular Routing enables navigation between different views in a single-page application. Router Guards are used to control navigation and protect routes. The advantages of using Angular Router Guards include:

• CanActivate: Controls whether a route can be activated.
• CanDeactivate: Controls whether a route can be deactivated.
• Resolve: Resolves data before a route is activated.

Router Guards help ensure that navigation occurs only when certain conditions are met, enhancing security and user experience.

10. Discuss the role of Angular Services in a modular and scalable application architecture. Provide examples of scenarios where services are essential.

Angular Services are singleton objects used for encapsulating and sharing logic and data between components. They play a crucial role in achieving a modular and scalable architecture. Scenarios where services are essential include:

• Data Sharing: Sharing data between components without direct coupling.
• Business Logic: Centralizing business logic to ensure consistency.
• HTTP Requests: Handling HTTP requests and providing a centralized point for API interactions.

Services enhance code reusability, maintainability, and testability in Angular applications.