Angular Developer interview questions

The best practices for implementing two-way data binding in Angular include using the built-in ngModel directive where appropriate, limiting two-way binding to simple forms and user inputs, leveraging one-way data flow for complex applications to enhance maintainability, and always ensuring that custom two-way bindings use the proper EventEmitter and property conventions (i.e., [property] and (propertyChange)).

Dependency injection enhances both testability and maintainability by allowing developers to inject required services or dependencies into components and classes, rather than hard-coding them. This enables easier unit testing by mocking dependencies and supports code reusability by managing dependencies at a central location.

Common pitfalls include unintentional memory leaks from unsubscribed observables, using inappropriate operators leading to performance issues, and not handling errors correctly. These can be avoided by using the async pipe in templates, leveraging operators like takeUntil for unsubscribing on component destruction, and always implementing robust error handling strategies.

Advanced patterns include implementing state management solutions like NgRx, using subjects and behavior subjects for component communication, leveraging selectors and effects for side-effect handling, and organizing state slices for scalability and testability.

Effective strategies include using shared services with RxJS subjects or observables for event emission, leveraging dependency injection to manage service instances at suitable module or component levels, and minimizing input/output chaining by adopting centralized state management when necessary.

To create custom two-way data binding, a developer should use the @Input decorator to bind a property and the @Output decorator with EventEmitter to emit changes. The component must follow the ‘property’ and ‘propertyChange’ naming convention, enabling the [(property)] syntax in the parent template.

Important considerations include ensuring service statelessness unless state sharing is required, providing services at the appropriate module or root level, using interfaces for abstraction, and utilizing Injectable scopes correctly for singleton or multiple instance requirements.

Performance can be optimized by minimizing synchronous subscriptions in components, using operators such as debounceTime, throttleTime, and distinctUntilChanged for user input handling, applying onPush change detection strategy, and preventing unnecessary emissions through proper use of RxJS operators.

A senior Angular developer handles complex asynchronous workflows by composing observables with higher-order RxJS operators such as switchMap, mergeMap, concatMap, and exhaustMap, utilizing forkJoin or combineLatest for parallel requests, and chaining operators for clean, readable code.

Approaches include using the RxJS tap operator for logging events, leveraging browser DevTools for performance profiling, employing libraries like rxjs-spy for inspecting observable streams, and ensuring all subscriptions are properly unsubscribed using takeUntil or the async pipe to prevent memory leaks.