What is Angular and how does it differ from AngularJS?
Angular is a TypeScript-based open-source framework for building web applications. Key differences from AngularJS include: component-based architecture instead of MVC, better performance with improved change detection, TypeScript usage, improved dependency injection, and modular development approach.
What are Angular decorators and list the most common ones?
Decorators are design patterns that modify JavaScript classes. Common Angular decorators include: @Component (defines component), @Injectable (defines service), @NgModule (defines module), @Input/@Output (property binding), @HostListener (DOM event binding), and @ViewChild (child component reference).
Explain the purpose of NgModule and its essential properties.
NgModule is a decorator that defines a module in Angular. Essential properties include: declarations (components, directives, pipes), imports (other modules), exports (shared declarations), providers (services), and bootstrap (root component). It helps organize application into cohesive blocks of functionality.
What is dependency injection in Angular and how does it work?
Dependency Injection is a design pattern where dependencies are provided to classes instead of creating them. Angular's DI system uses @Injectable decorator, providers array, and hierarchical injector tree. It manages object creation, lifetime, and dependencies, promoting loose coupling and testability.
What are lifecycle hooks in Angular? List and explain the major ones.
Lifecycle hooks are methods that Angular calls on components/directives at specific moments. Major hooks: ngOnInit (after first ngOnChanges), ngOnChanges (when data-bound property changes), ngOnDestroy (before destruction), ngDoCheck (during change detection), ngAfterViewInit (after view initialization).
What is the difference between constructor and ngOnInit?
Constructor is a TypeScript feature called when class is instantiated, used for dependency injection. ngOnInit is an Angular lifecycle hook called after data-bound properties are initialized. Best practice: use constructor for DI setup, ngOnInit for initialization logic.
Explain change detection in Angular.
Change detection is Angular's process of synchronizing component model and view. Uses Zone.js to track async operations. Two strategies: Default (checks entire tree) and OnPush (only checks on reference changes). Can be optimized using immutability and proper component architecture.
What is data binding in Angular and what are its types?
Data binding synchronizes component and view. Types: Interpolation {{data}}, Property binding [property], Event binding (event), Two-way binding [(ngModel)]. Enables automatic sync between model and view, reducing manual DOM manipulation.
What is the purpose of ViewChild and ViewChildren decorators?
ViewChild/ViewChildren decorators provide access to child elements in component template. ViewChild returns single element, ViewChildren returns QueryList. Used for accessing child components, directives, or DOM elements. Important for component interaction.
What are Angular services and why are they used?
Services are singleton objects used for sharing data/functionality across components. Marked with @Injectable decorator. Used for: data sharing, business logic, external interactions (HTTP calls). Promotes DRY principle and separation of concerns.
Explain the difference between providedIn and providers array.
providedIn configures service scope in @Injectable decorator (root, platform, any, specific module). providers array in @NgModule registers services at module level. providedIn enables tree-shaking, preferred for service registration in modern Angular.
What is content projection in Angular?
Content projection (ng-content) allows passing content from parent to child component. Supports single-slot and multi-slot projection. Uses select attribute for targeted projection. Important for creating reusable, flexible components.
What are Angular templates and their key features?
Templates define component's view in HTML with Angular-specific syntax. Features: data binding, directives, pipes, template expressions, template statements. Supports structural directives (*ngIf, *ngFor), event binding, and property binding.
What is AOT compilation and its benefits?
Ahead-of-Time compilation compiles Angular application at build time. Benefits: faster rendering, smaller download size, earlier template error detection, better security. Default in production builds since Angular 9.
Explain Angular's hierarchical dependency injection system.
Angular DI uses hierarchical injector tree: NullInjector (root), Platform, Module, Element (component/directive). Child injectors inherit from parents. Enables service scope control, instance sharing, and override mechanisms.
What are template reference variables?
Template reference variables (#var) create references to DOM elements, components, or directives in template. Used for direct access in template or component class via ViewChild. Useful for form handling and component interaction.
How does zone.js work in Angular?
Zone.js provides execution context tracking for async operations. Angular uses it for automatic change detection by patching async operations. Enables detection of state changes from events, HTTP, timers. Critical for Angular's change detection system.
What is the difference between declarations, imports, and providers in NgModule?
declarations list components/directives/pipes belonging to module. imports list other modules needed. providers list services for dependency injection. declarations must be unique across app, imports can be shared, providers affect dependency injection scope.
What are Angular elements and their use cases?
Angular elements are Angular components packaged as custom elements (Web Components). Use cases: embedding Angular components in non-Angular applications, micro-frontends, widget development. Enables framework-agnostic component reuse.
Explain component communication methods in Angular.
Methods include: @Input/@Output decorators, services (state management), ViewChild/ContentChild, event emitters, subject/behavior subject, parent-child interaction. Choose based on component relationship and data flow requirements.
What is the difference between pure and impure pipes?
Pure pipes execute only when input value reference changes. Impure pipes execute on every change detection cycle. Pure pipes better for performance, impure needed for dynamic transformations. Default is pure, impure marked with pure: false.
How does Angular handle module bundling and lazy loading?
Angular CLI uses webpack for bundling. Lazy loading implemented through RouterModule with loadChildren syntax. Reduces initial bundle size, improves load time. Modules loaded on-demand when route accessed.
What is the purpose of the async pipe?
Async pipe automatically subscribes/unsubscribes to observables/promises in templates. Handles subscription lifecycle, prevents memory leaks. Useful for handling async data in templates without manual subscription management.
What are host bindings and host listeners?
HostBinding decorates properties to bind to host element properties. HostListener decorates methods to handle host element events. Used in directives/components for DOM interaction without direct manipulation.
How does Angular handle error handling and error boundaries?
Error handling through: try-catch blocks, RxJS catchError operator, HTTP interceptors, ErrorHandler class, Router error handling. No direct equivalent to React error boundaries. Global error handling configured in module providers.
What is the ViewEncapsulation and its types?
ViewEncapsulation controls component CSS encapsulation. Types: Emulated (default, scoped CSS), None (global CSS), ShadowDom (true shadow DOM). Affects how component styles are applied and scoped in application.
What are Angular schematics?
Schematics are templates for generating/modifying code. Used by Angular CLI for scaffolding components, services, etc. Can create custom schematics for project-specific generators. Supports workspace modifications.
How does Angular handle component styling?
Component styles defined in styles/styleUrls properties. Supports CSS encapsulation through ViewEncapsulation. Can use preprocessors (SCSS/SASS), CSS variables, global styles. Styles scoped to component by default.
What is the purpose of NgZone service?
NgZone service provides access to Angular's zone for executing work inside/outside Angular's zone. Used for performance optimization, manual change detection control. Important for integrating with third-party libraries.
How does Angular handle internationalization (i18n)?
Angular i18n uses XLF/XLIFF files for translations. Supports: text extraction, pluralization, date/number formatting, runtime language switching. Built-in i18n pipes, can use ngx-translate library for dynamic translations.
What is the Angular Router and its core features?
Angular Router enables navigation between views. Core features include: path-based routing, child routes, route parameters, guards, lazy loading, route resolvers, navigation events, and location strategies. Configured in RouterModule using Routes array.
Explain route guards and list different types.
Route guards control route access/behavior. Types: CanActivate (access control), CanDeactivate (leaving control), CanLoad (lazy loading control), CanActivateChild (child route access), Resolve (pre-fetch data). Implement as services using specific interfaces.
How do you implement lazy loading in Angular routes?
Lazy loading implemented using loadChildren syntax in route configuration: path: 'admin', loadChildren: () => import('./admin/admin.module').then(m => m.AdminModule). Improves initial load time by loading modules on demand.
What are route parameters and how are they handled?
Route parameters pass data through URL. Types: Required parameters (:id), Optional parameters (?id=), Query parameters (?key=value). Accessed using ActivatedRoute service through params, queryParams, or paramMap observables.
Explain route resolvers and their use cases.
Resolvers pre-fetch data before route activation. Implement Resolve interface in service. Use cases: loading required data before showing view, preventing partial/loading views, handling dependencies. Returns data/observable/promise.
What are child routes and how are they configured?
Child routes create hierarchical route structures. Configured using children property in route configuration. Requires router-outlet in parent component. Enables feature modules, nested routing, and component reuse.
How do you handle route events in Angular?
Route events monitored using Router.events observable. Events include: NavigationStart, NavigationEnd, NavigationError, etc. Used for loading indicators, analytics, navigation tracking. Subscribe in component/service.
What are the different navigation methods in Angular?
Navigation methods: router.navigate([path]), routerLink directive, router.navigateByUrl(url). navigate/navigateByUrl programmatic, routerLink template-based. Support parameters, query params, fragments, relative/absolute paths.
Explain location strategies in Angular routing.
Location strategies: PathLocationStrategy (default, uses HTML5 History API, clean URLs), HashLocationStrategy (uses hash URLs). Configure in RouterModule.forRoot() options. Affects URL format and server configuration requirements.
How do you handle 404 (Not Found) routes?
404 routes configured using wildcard path '**' as last route in configuration. Redirects to specific component/path when no other routes match. Important for user experience and error handling.
What is route reuse strategy and its implementation?
RouteReuseStrategy controls component reuse during navigation. Custom implementation can define when to store/reuse components. Improves performance by avoiding recreation. Configure in providers array.
How do you implement authentication guards?
Authentication guards implement CanActivate interface. Check authentication state, redirect unauthorized access. Often use authentication service, router service. Return boolean/UrlTree/Promise/Observable determining access.
What are auxiliary routes in Angular?
Auxiliary routes (named router outlets) allow multiple independent routes. Use named router-outlet. Enable side-by-side views, independent navigation. Configured with outlet property in route definition.
How do you preserve query parameters during navigation?
Query parameters preserved using queryParamsHandling option in navigation methods/routerLink. Values: 'merge' (combine), 'preserve' (keep current). Important for maintaining state during navigation.
What is the difference between paramMap and params in ActivatedRoute?
paramMap is newer, immutable, provides has()/get() methods. params is older, direct object access. paramMap recommended for type safety and null checking. Both available as observable and snapshot.
How do you implement nested routing with named outlets?
Named outlets allow multiple router-outlets with unique names. Configure routes with outlet property. Enable complex layouts, independent navigation flows. Useful for master-detail views, sidebars.
What are the best practices for Angular routing?
Best practices: module-based routing, lazy loading, proper guard implementation, consistent naming, error handling, loading indicators, proper parameter handling. Consider security, performance, user experience.
How do you handle route data and static data?
Route data configured using data property in route definition. Static data accessed via ActivatedRoute.data observable. Useful for titles, metadata, configuration. Available in components and guards.
What is router state and how to access it?
Router state contains current route tree information. Accessed using Router.routerState or ActivatedRoute. Provides information about active routes, parameters, data. Useful for complex navigation scenarios.
How do you implement breadcrumbs using Angular routing?
Breadcrumbs implemented using router state/events. Track active route path, extract route data. Consider nested routes, dynamic segments. Update on navigation events. Important for navigation UX.
What is the purpose of CanDeactivate guard?
CanDeactivate prevents leaving route without confirmation. Common for forms, unsaved changes. Returns boolean/Promise/Observable. Implements confirmation dialogs, state checks. Important for data loss prevention.
How do you handle route transitions and animations?
Route transitions implemented using Angular animations. Trigger on router-outlet, use route data. Consider enter/leave states, timing. Enhance user experience through smooth transitions.
What is the difference between absolute and relative routing?
Absolute paths start with '/', relative paths based on current route. Relative navigation uses '../' for parent routes. Choose based on navigation context. Affects route configuration and navigation methods.
How do you handle route redirects?
Redirects configured using redirectTo property in route definition. Support path matching, parameters. Used for default routes, URL normalization. Can be absolute or relative paths.
What is router link active and its usage?
routerLinkActive adds class when route active. Configure with exact match option. Useful for navigation highlighting, active state styling. Supports multiple classes, custom logic.
How do you implement role-based routing?
Role-based routing uses guards checking user roles/permissions. Combine with authentication guard, role service. Return boolean/UrlTree for access control. Important for security, user experience.
What are matrix parameters in Angular routing?
Matrix parameters are URL segments with key-value pairs. Format: path;key=value. Alternative to query parameters. Accessed through paramMap. Useful for state preservation, filtering.
How do you implement route caching?
Route caching through RouteReuseStrategy. Store component state, reuse on navigation. Consider memory usage, state management. Useful for performance optimization, state preservation.
What is the purpose of path matching strategies?
Path matching strategies control route matching behavior. Options: prefix (default, matches start), full (exact match). Configure in route definition. Affects route resolution, order importance.
How do you handle navigation failure?
Navigation failures handled through Router.events or navigation promise rejection. Implement error handling, user feedback. Consider redirection, retry logic. Important for robust navigation.
What are the two types of forms in Angular and their key differences?
Angular has Template-driven forms (simple, directive based, async validation) and Reactive forms (complex, explicit, synchronous validation). Template-driven forms use two-way binding with ngModel, while Reactive forms use FormGroup/FormControl with explicit form model.
How do you implement form validation in Reactive forms?
Reactive form validation uses validators in FormControl/FormGroup construction. Built-in validators (required, minLength, pattern) or custom validators. Status and error states tracked through form control properties. Synchronous and async validation supported.
What are form controls and form groups in Angular?
FormControl tracks value/validation of individual form field. FormGroup groups related controls together, tracks aggregate value/status. Both provide value changes observables, validation state, methods for value updates.
How do you create custom validators in Angular?
Custom validators are functions returning validation errors or null. Can be synchronous (ValidatorFn) or asynchronous (AsyncValidatorFn). Implement for complex validation logic. Can access external services, combine multiple validations.
What are form arrays and their use cases?
FormArray manages collection of form controls/groups dynamically. Used for variable-length form fields (dynamic forms, multiple items). Provides array-like API for manipulation. Common in dynamic questionnaires, product lists.
How do you handle form submission in Angular?
Form submission handled through ngSubmit event or form's submit method. Implement validation checks, disable submit during processing, handle success/error responses. Consider loading states, user feedback, form reset.
What are the different form states and how to track them?
Form states include: pristine/dirty, touched/untouched, valid/invalid, pending. Tracked through form control properties and CSS classes. Used for validation feedback, UI updates. Available at control and form level.
How do you implement cross-field validation?
Cross-field validation implemented through form group validators. Access multiple control values, compare fields (password confirmation). Can use custom validators at group level. Important for related field validation.
What are async validators and their implementation?
Async validators perform validation asynchronously (API calls, database checks). Return Promise/Observable. Used for unique email/username validation. Handle pending state, implement debounce time. Consider error handling.
How do you reset forms in Angular?
Forms reset using reset() method on FormGroup/FormControl. Can provide initial values, reset specific controls. Resets both values and validation states. Consider UI feedback, data preservation needs.
What are form builders and their advantages?
FormBuilder service provides syntactic sugar for creating form controls. Simplifies complex form creation, reduces boilerplate. Methods include control(), group(), array(). Improves code readability and maintenance.
How do you handle file uploads in Angular forms?
File uploads handled through input type='file' and FormData. Use change event to capture files, implement validation (size, type). Consider progress tracking, multiple file handling, chunked uploads.
What are value changes and status changes in forms?
valueChanges and statusChanges are observables tracking form changes. valueChanges emits new values, statusChanges emits validation status. Used for reactive form updates, validation feedback. Support filtering, debouncing.
How do you implement conditional validation?
Conditional validation changes validation rules based on conditions. Implement through setValidators(), clearValidators(). Update validators dynamically based on form values/state. Consider validation dependencies.
What are form control wrappers and their use?
Form control wrappers are custom components wrapping form controls. Provide reusable validation, styling, behavior. Implement ControlValueAccessor interface. Common for custom input components, complex controls.
How do you handle form arrays validation?
Form arrays validation applies at array and item levels. Validate array length, individual controls. Can implement custom validators for array-specific rules. Consider dynamic validation updates, error aggregation.
What is the purpose of updateOn property in forms?
updateOn controls when form control updates (change, blur, submit). Affects validation timing, value updates. Configurable at control/group level. Important for performance, user experience optimization.
How do you implement custom error messages?
Custom error messages handled through error states in template. Access errors through control.errors property. Can use error message service, translation support. Consider message formatting, multiple errors.
What are the best practices for form validation?
Best practices: immediate feedback, clear error messages, consistent validation, proper error states, accessibility support. Consider user experience, performance, maintainability. Implement proper error handling.
How do you implement dynamic forms?
Dynamic forms built using form arrays/groups, metadata-driven approach. Generate controls from configuration/data. Consider validation rules, field dependencies. Important for configurable forms, surveys.
What is the role of ngModel in template-driven forms?
ngModel provides two-way data binding in template-driven forms. Creates form controls implicitly, tracks value/validation state. Requires FormsModule. Limited compared to reactive forms' explicit control.
How do you handle form submission errors?
Form submission errors handled through error callbacks, error states. Display user-friendly messages, highlight affected fields. Consider error types, recovery options. Implement proper error handling patterns.
What are nested form groups and their implementation?
Nested form groups organize related controls hierarchically. Created using FormBuilder.group() nesting. Support complex form structures, modular validation. Common in address forms, complex data entry.
How do you implement form validation messages?
Validation messages implemented through template logic, error states. Can use validation message service, localization support. Consider message context, multiple languages. Important for user feedback.
What is dirty checking in Angular forms?
Dirty checking tracks form value changes. pristine/dirty states indicate modifications. Used for save prompts, reset functionality. Important for tracking user interactions, form state management.
How do you implement form array validation patterns?
Form array validation patterns include: min/max items, unique values, dependent validations. Implement through custom validators, array-level validation. Consider complex validation scenarios, error aggregation.
What are the common form validation patterns?
Common patterns: required fields, email format, password strength, numeric ranges, custom regex. Implement through built-in/custom validators. Consider user experience, security requirements.
How do you handle form state persistence?
Form state persistence through services, local storage, state management. Consider autosave functionality, recovery options. Important for long forms, multi-step processes. Implement proper cleanup.
What are form control events and their handling?
Form control events include: valueChanges, statusChanges, focus/blur events. Handle through event bindings, observables. Used for validation feedback, dependent updates. Consider event ordering, performance.
How do you implement multi-step form validation?
Multi-step validation through form groups per step, wizard pattern. Validate each step, track completion status. Consider state management, navigation rules. Important for complex workflows.
What are the two types of forms in Angular and their key differences?
Angular has Template-driven forms (simple, directive based, async validation) and Reactive forms (complex, explicit, synchronous validation). Template-driven forms use two-way binding with ngModel, while Reactive forms use FormGroup/FormControl with explicit form model.
How do you implement form validation in Reactive forms?
Reactive form validation uses validators in FormControl/FormGroup construction. Built-in validators (required, minLength, pattern) or custom validators. Status and error states tracked through form control properties. Synchronous and async validation supported.
What are form controls and form groups in Angular?
FormControl tracks value/validation of individual form field. FormGroup groups related controls together, tracks aggregate value/status. Both provide value changes observables, validation state, methods for value updates.
How do you create custom validators in Angular?
Custom validators are functions returning validation errors or null. Can be synchronous (ValidatorFn) or asynchronous (AsyncValidatorFn). Implement for complex validation logic. Can access external services, combine multiple validations.
What are form arrays and their use cases?
FormArray manages collection of form controls/groups dynamically. Used for variable-length form fields (dynamic forms, multiple items). Provides array-like API for manipulation. Common in dynamic questionnaires, product lists.
How do you handle form submission in Angular?
Form submission handled through ngSubmit event or form's submit method. Implement validation checks, disable submit during processing, handle success/error responses. Consider loading states, user feedback, form reset.
What are the different form states and how to track them?
Form states include: pristine/dirty, touched/untouched, valid/invalid, pending. Tracked through form control properties and CSS classes. Used for validation feedback, UI updates. Available at control and form level.
How do you implement cross-field validation?
Cross-field validation implemented through form group validators. Access multiple control values, compare fields (password confirmation). Can use custom validators at group level. Important for related field validation.
What are async validators and their implementation?
Async validators perform validation asynchronously (API calls, database checks). Return Promise/Observable. Used for unique email/username validation. Handle pending state, implement debounce time. Consider error handling.
How do you reset forms in Angular?
Forms reset using reset() method on FormGroup/FormControl. Can provide initial values, reset specific controls. Resets both values and validation states. Consider UI feedback, data preservation needs.
What are form builders and their advantages?
FormBuilder service provides syntactic sugar for creating form controls. Simplifies complex form creation, reduces boilerplate. Methods include control(), group(), array(). Improves code readability and maintenance.
How do you handle file uploads in Angular forms?
File uploads handled through input type='file' and FormData. Use change event to capture files, implement validation (size, type). Consider progress tracking, multiple file handling, chunked uploads.
What are value changes and status changes in forms?
valueChanges and statusChanges are observables tracking form changes. valueChanges emits new values, statusChanges emits validation status. Used for reactive form updates, validation feedback. Support filtering, debouncing.
How do you implement conditional validation?
Conditional validation changes validation rules based on conditions. Implement through setValidators(), clearValidators(). Update validators dynamically based on form values/state. Consider validation dependencies.
What are form control wrappers and their use?
Form control wrappers are custom components wrapping form controls. Provide reusable validation, styling, behavior. Implement ControlValueAccessor interface. Common for custom input components, complex controls.
How do you handle form arrays validation?
Form arrays validation applies at array and item levels. Validate array length, individual controls. Can implement custom validators for array-specific rules. Consider dynamic validation updates, error aggregation.
What is the purpose of updateOn property in forms?
updateOn controls when form control updates (change, blur, submit). Affects validation timing, value updates. Configurable at control/group level. Important for performance, user experience optimization.
How do you implement custom error messages?
Custom error messages handled through error states in template. Access errors through control.errors property. Can use error message service, translation support. Consider message formatting, multiple errors.
What are the best practices for form validation?
Best practices: immediate feedback, clear error messages, consistent validation, proper error states, accessibility support. Consider user experience, performance, maintainability. Implement proper error handling.
How do you implement dynamic forms?
Dynamic forms built using form arrays/groups, metadata-driven approach. Generate controls from configuration/data. Consider validation rules, field dependencies. Important for configurable forms, surveys.
What is the role of ngModel in template-driven forms?
ngModel provides two-way data binding in template-driven forms. Creates form controls implicitly, tracks value/validation state. Requires FormsModule. Limited compared to reactive forms' explicit control.
How do you handle form submission errors?
Form submission errors handled through error callbacks, error states. Display user-friendly messages, highlight affected fields. Consider error types, recovery options. Implement proper error handling patterns.
What are nested form groups and their implementation?
Nested form groups organize related controls hierarchically. Created using FormBuilder.group() nesting. Support complex form structures, modular validation. Common in address forms, complex data entry.
How do you implement form validation messages?
Validation messages implemented through template logic, error states. Can use validation message service, localization support. Consider message context, multiple languages. Important for user feedback.
What is dirty checking in Angular forms?
Dirty checking tracks form value changes. pristine/dirty states indicate modifications. Used for save prompts, reset functionality. Important for tracking user interactions, form state management.
How do you implement form array validation patterns?
Form array validation patterns include: min/max items, unique values, dependent validations. Implement through custom validators, array-level validation. Consider complex validation scenarios, error aggregation.
What are the common form validation patterns?
Common patterns: required fields, email format, password strength, numeric ranges, custom regex. Implement through built-in/custom validators. Consider user experience, security requirements.
How do you handle form state persistence?
Form state persistence through services, local storage, state management. Consider autosave functionality, recovery options. Important for long forms, multi-step processes. Implement proper cleanup.
What are form control events and their handling?
Form control events include: valueChanges, statusChanges, focus/blur events. Handle through event bindings, observables. Used for validation feedback, dependent updates. Consider event ordering, performance.
How do you implement multi-step form validation?
Multi-step validation through form groups per step, wizard pattern. Validate each step, track completion status. Consider state management, navigation rules. Important for complex workflows.
What is HttpClient in Angular and its key features?
HttpClient is Angular's built-in HTTP client. Features: typed responses, observables for requests, interceptors support, progress events, error handling. Provides methods for HTTP operations (get, post, put, delete). Supports request/response transformation.
What are HTTP Interceptors and their use cases?
Interceptors intercept and modify HTTP requests/responses. Use cases: authentication headers, error handling, loading indicators, caching, logging. Implement HttpInterceptor interface. Can be chained, order matters.
How do you handle error responses in HttpClient?
Error handling through catchError operator, error interceptors. Implement global/local error handlers, retry logic. Consider error types (network, server, client), user feedback. Use ErrorHandler class for global handling.
What are the best practices for API service architecture?
Best practices: separate service layer, typed interfaces, proper error handling, environment configuration. Consider request caching, retry strategies, cancellation. Implement proper separation of concerns.
How do you implement request caching?
Caching implemented through interceptors, services. Use shareReplay operator, cache storage. Consider cache invalidation, freshness checks. Important for performance optimization, offline support.
What are HttpParams and their usage?
HttpParams manage URL parameters in requests. Immutable object for query parameters. Methods: set(), append(), delete(). Important for API queries, filtering. Consider parameter encoding, multiple values.
How do you handle file uploads using HttpClient?
File uploads using FormData, multipart/form-data content type. Support progress events, cancellation. Consider file size limits, validation. Implement proper error handling, progress tracking.
What is request cancellation and its implementation?
Request cancellation using takeUntil operator, AbortController. Implement cleanup on component destruction. Important for preventing memory leaks, unnecessary requests. Consider loading states.
How do you handle authentication in HTTP requests?
Authentication through interceptors, auth headers. Implement token management, refresh logic. Consider session handling, secure storage. Important for secured APIs, user sessions.
What are HTTP headers and their management?
Headers managed through HttpHeaders class. Set content type, authorization, custom headers. Immutable object, chainable methods. Consider CORS, security headers. Important for API communication.
How do you implement retry logic for failed requests?
Retry logic using retry/retryWhen operators. Configure retry count, delay. Consider error types, backoff strategy. Important for handling temporary failures, network issues.
What are progress events and their handling?
Progress events track upload/download progress. Use reportProgress option, HttpEventType. Implement progress indicators, cancellation. Important for large file operations, user feedback.
How do you handle concurrent requests?
Concurrent requests using forkJoin, combineLatest operators. Consider error handling, loading states. Important for dependent data, parallel operations. Implement proper request management.
What is CORS and how to handle it?
CORS (Cross-Origin Resource Sharing) handled through server configuration, proxy settings. Configure allowed origins, methods, headers. Consider security implications, browser restrictions. Important for cross-domain requests.
How do you implement API versioning in Angular?
API versioning through URL prefixes, headers, interceptors. Configure base URLs, version management. Consider backward compatibility, migration strategy. Important for API evolution.
What are HTTP request timeouts?
Timeouts configured using timeout operator, request configuration. Consider network conditions, server response time. Important for user experience, error handling. Implement proper feedback.
How do you handle offline support and synchronization?
Offline support through service workers, local storage. Implement queue system, sync logic. Consider conflict resolution, data persistence. Important for offline-first applications.
What are HTTP response types and their handling?
Response types: json, text, blob, arrayBuffer. Configure using responseType option. Consider data format, transformation needs. Important for different content types, file downloads.
How do you implement API mocking for development?
API mocking through interceptors, mock services. Configure development environment, test data. Consider realistic scenarios, error cases. Important for development, testing.
What are the security considerations for API calls?
Security considerations: XSS prevention, CSRF protection, secure headers. Implement authentication, authorization. Consider data encryption, input validation. Important for application security.
How do you handle large data sets in API responses?
Large data handling through pagination, infinite scroll. Implement virtual scrolling, data chunking. Consider performance impact, memory usage. Important for scalable applications.
What is request debouncing and its implementation?
Debouncing delays request execution until pause in triggering. Implement using debounceTime operator. Consider user input, search functionality. Important for performance optimization.
How do you implement API error mapping?
Error mapping through interceptors, error services. Transform server errors to application format. Consider error categorization, localization. Important for consistent error handling.
What are WebSockets and their integration?
WebSockets enable real-time communication. Implement using socket.io, custom services. Consider connection management, reconnection logic. Important for real-time features.
How do you handle API rate limiting?
Rate limiting through interceptors, request queuing. Implement backoff strategy, request prioritization. Consider server limits, user experience. Important for API consumption.
What is request/response transformation?
Transformation through interceptors, map operator. Modify request/response data format. Consider data consistency, type safety. Important for API integration.
How do you implement API request queueing?
Request queueing through custom services, RxJS operators. Handle sequential requests, priorities. Consider error handling, cancellation. Important for dependent operations.
What are the best practices for API testing?
Testing practices: unit tests for services, mock interceptors, integration tests. Consider error scenarios, async testing. Important for reliability, maintenance.
How do you handle API documentation?
Documentation through Swagger/OpenAPI, custom documentation. Generate TypeScript interfaces, API services. Consider versioning, maintenance. Important for development workflow.
What is Change Detection in Angular and how does it affect performance?
Change Detection determines UI updates based on data changes. Default strategy checks all components, OnPush checks only on reference changes. Improper implementation can cause performance issues. Optimize using immutable objects, pure pipes, OnPush strategy.
How does Lazy Loading improve application performance?
Lazy Loading loads modules on demand, reducing initial bundle size. Implemented through routing configuration using loadChildren. Improves initial load time, reduces memory usage. Consider module boundaries, preloading strategies.
What is AOT compilation and its performance benefits?
Ahead-of-Time compilation compiles templates during build. Benefits: faster rendering, smaller payload, earlier error detection. Default in production builds. Eliminates need for template compiler in runtime.
How do you optimize memory usage in Angular applications?
Memory optimization through: proper unsubscription from observables, avoiding memory leaks, cleaning up event listeners, implementing trackBy for ngFor. Consider component lifecycle, large data handling.
What is the purpose of trackBy function in ngFor?
trackBy provides unique identifier for items in ngFor. Helps Angular track items efficiently, reduces DOM operations. Improves performance with large lists, frequent updates. Customize based on data structure.
How do you implement virtual scrolling in Angular?
Virtual scrolling renders only visible items using ScrollingModule. Improves performance with large lists. Configure through CDK virtual scroll viewport. Consider item size, buffer size, scroll strategy.
What are pure and impure pipes in Angular?
Pure pipes execute only on input changes, impure on every change detection. Pure pipes better for performance, cache results. Use impure pipes sparingly. Consider transformation complexity, update frequency.
How do you optimize bundle size in Angular?
Bundle optimization through: tree shaking, lazy loading, proper imports, removing unused dependencies. Use built-in optimization flags, analyze bundles. Consider code splitting, dynamic imports.
What is Tree Shaking and its importance?
Tree Shaking removes unused code from final bundle. Enabled by default in production builds. Requires proper module imports, side-effect free code. Important for reducing application size.
How do you implement caching in Angular applications?
Caching implemented through services, HTTP interceptors. Cache API responses, computed values, static assets. Consider cache invalidation, storage limits. Important for reducing server requests.
What are Web Workers and their usage in Angular?
Web Workers run scripts in background threads. Offload heavy computations, improve responsiveness. Implement using Angular CLI generation. Consider data transfer overhead, use cases.
How do you optimize Angular forms for performance?
Form optimization through: proper validation timing, minimal form controls, efficient value updates. Consider updateOn option, form structure. Important for complex forms, frequent updates.
What is the role of enableProdMode in Angular?
enableProdMode disables development checks and warnings. Improves performance in production. Call before bootstrapping application. Important for production deployments.
How do you implement preloading strategies?
Preloading loads modules after initial load. Configure through PreloadAllModules or custom strategy. Balance between performance and resource usage. Consider user patterns, network conditions.
What are the best practices for performance optimization?
Best practices: proper change detection, lazy loading, AOT compilation, bundle optimization, caching implementation. Regular performance audits, monitoring. Consider user experience, metrics.
How do you implement server-side rendering (SSR)?
SSR using Angular Universal. Improves initial load, SEO. Configure through Angular CLI commands. Consider hydration, state transfer. Important for SEO-critical applications.
What is differential loading in Angular?
Differential loading serves modern/legacy bundles based on browser support. Reduces bundle size for modern browsers. Enabled by default in new projects. Consider browser support requirements.
How do you optimize images in Angular applications?
Image optimization through: lazy loading, proper sizing, format selection, CDN usage. Implement loading attribute, responsive images. Consider bandwidth usage, caching strategies.
What is Angular Ivy and its performance benefits?
Ivy is Angular's rendering engine. Benefits: smaller bundles, faster compilation, better debugging. Default since Angular 9. Enables tree-shakable components, improved build optimization.
How do you implement performance monitoring?
Performance monitoring through: browser dev tools, Angular profiler, custom metrics. Track key indicators, implement logging. Consider user metrics, error tracking. Important for continuous optimization.
What are performance budgets in Angular?
Performance budgets set size limits for bundles. Configure in angular.json. Enforce during build process. Consider different types (bundle, initial), thresholds. Important for maintaining performance.
How do you optimize router navigation?
Router optimization through: preloading strategies, route guards optimization, minimal route data. Consider navigation timing, caching. Important for smooth user experience.
What is the importance of code splitting?
Code splitting divides code into smaller chunks. Improves initial load time, enables lazy loading. Implement through route-level splitting, dynamic imports. Consider bundle size, loading strategy.
How do you optimize third-party library usage?
Library optimization through: selective imports, lazy loading, alternatives evaluation. Consider bundle impact, necessity. Important for maintaining lean application.
What is the role of service workers in performance?
Service workers enable offline capabilities, caching. Improve load times, reduce server load. Configure through Angular PWA package. Consider cache strategies, update flow.
How do you implement infinite scrolling efficiently?
Efficient infinite scrolling through: virtual scrolling, data chunking, proper cleanup. Consider memory management, loading states. Important for large data sets.
What are the common performance bottlenecks?
Common bottlenecks: excessive change detection, large bundles, unoptimized images, memory leaks. Identify through profiling, monitoring. Consider regular performance audits.
How do you optimize Angular Material usage?
Material optimization through: selective imports, lazy loading components, proper theming. Consider bundle size impact, usage patterns. Important for Material-based applications.
What is the impact of Zone.js on performance?
Zone.js affects change detection performance. Consider zone-less operations, manual change detection. Optimize through proper zone usage, async operations. Important for application responsiveness.
What are the different types of testing in Angular applications?
Angular supports: Unit Testing (isolated component/service testing), Integration Testing (component interactions), E2E Testing (full application flow). Uses Jasmine framework, Karma test runner, Protractor/Cypress for E2E.
How do you test components in Angular?
Component testing using TestBed, ComponentFixture. Test isolated logic, template bindings, component interactions. Mock dependencies, simulate events. Use shallow/deep rendering based on needs.
What is TestBed and its role in Angular testing?
TestBed is primary API for unit testing. Configures testing module, creates components, provides dependencies. Methods include configureTestingModule(), createComponent(). Essential for component/service testing.
How do you test services in Angular?
Service testing through TestBed injection, isolated testing. Mock dependencies, test methods/properties. Use dependency injection, spies for external services. Test async operations using fakeAsync/tick.
What are spies in Jasmine and their usage?
Spies mock method behavior, track calls. Created using spyOn(), createSpy(). Track method calls, arguments, return values. Essential for mocking dependencies, verifying interactions.
How do you test HTTP requests?
HTTP testing using HttpTestingController. Mock requests/responses, verify request parameters. Test success/error scenarios, multiple requests. Important for API integration testing.
What is async testing in Angular?
Async testing handles asynchronous operations. Use async/fakeAsync/waitForAsync helpers. Test promises, observables, timers. Important for testing real-world scenarios.
How do you test directives?
Directive testing through component creation, DOM manipulation. Test directive behavior, inputs/outputs. Create test host components. Consider element interactions, lifecycle hooks.
What is E2E testing and its implementation?
E2E testing verifies full application flow. Implemented using Protractor/Cypress. Test user scenarios, navigation, interactions. Important for regression testing, feature verification.
How do you test pipes in Angular?
Pipe testing through isolated tests, transformation verification. Test with different inputs, edge cases. Consider pure/impure pipes, parameter handling. Simple to test due to pure function nature.
What are test doubles and their types?
Test doubles include: Spies, Stubs, Mocks, Fakes, Dummies. Used for isolating components, controlling dependencies. Choose based on testing needs, complexity. Important for unit testing.
How do you test routes and navigation?
Route testing using RouterTestingModule, Location service. Test navigation, route parameters, guards. Mock router service, verify navigation calls. Important for application flow testing.
What is code coverage and its importance?
Code coverage measures tested code percentage. Generated using ng test --code-coverage. Track statements, branches, functions coverage. Important for quality assurance, identifying untested code.
How do you test forms in Angular?
Form testing through ReactiveFormsModule/FormsModule. Test form validation, value changes, submissions. Simulate user input, verify form state. Consider complex validation scenarios.
What are the best practices for unit testing?
Best practices: arrange-act-assert pattern, single responsibility tests, proper isolation, meaningful descriptions. Consider test maintainability, readability. Follow testing pyramid principles.
How do you test error scenarios?
Error testing through exception throwing, error handling verification. Test error states, recovery mechanisms. Consider different error types, user feedback. Important for robustness.
What is component integration testing?
Integration testing verifies component interactions. Test parent-child communications, service integration. Use TestBed for configuration, fixture for interaction. Consider component relationships.
How do you test observables and subscriptions?
Observable testing using marbles, fakeAsync. Test stream behavior, error handling. Consider unsubscription, memory leaks. Important for reactive programming testing.
What is shallow vs deep testing?
Shallow testing renders component without children, deep includes child components. Choose based on testing scope, complexity. Consider component dependencies, testing goals.
How do you test NgRx store?
NgRx testing through TestStore, mock store. Test actions, reducers, effects separately. Consider state changes, async operations. Important for state management testing.
What are test fixtures and their usage?
Fixtures provide component testing environment. Created using TestBed.createComponent(). Access component instance, debug element. Essential for component testing, DOM interaction.
How do you test component lifecycle hooks?
Lifecycle testing through hook method spies, state verification. Test initialization, destruction logic. Consider timing, dependencies. Important for component behavior testing.
What is snapshot testing?
Snapshot testing compares component output with stored snapshot. Useful for UI regression testing. Consider update process, maintenance. Important for template stability.
How do you test custom events?
Custom event testing through EventEmitter simulation, output binding. Test event emission, handler execution. Consider event payload, timing. Important for component interaction.
What are the common testing patterns?
Common patterns: setup/teardown, data builders, test utilities, shared configurations. Consider reusability, maintenance. Important for testing efficiency, consistency.
How do you test async validators?
Async validator testing through fakeAsync, tick. Mock validation service, test timing. Consider error cases, loading states. Important for form validation testing.
What is test isolation and its importance?
Test isolation ensures tests run independently. Reset state between tests, mock dependencies. Consider test order, shared resources. Important for reliable testing.
How do you test error boundaries?
Error boundary testing through error triggering, recovery verification. Test error handling components, fallback UI. Consider different error scenarios, user experience.
What are test harnesses and their benefits?
Test harnesses provide component interaction API. Simplify component testing, abstract DOM details. Used in Angular Material testing. Important for complex component testing.
What is Cross-Site Scripting (XSS) and how to prevent it in Angular?
XSS attacks inject malicious scripts. Angular prevents by default through automatic sanitization of HTML, style bindings. Use DomSanitizer for trusted content, avoid bypass methods. Implement Content Security Policy (CSP).
How does Angular handle CSRF/XSRF protection?
Angular includes built-in CSRF/XSRF protection using double-submit cookie pattern. Automatically adds XSRF-TOKEN cookie to requests. Configure through HttpClientXsrfModule. Server must support token validation.
What is Content Security Policy (CSP) in Angular?
CSP restricts resource loading, prevents attacks. Configure through meta tags or HTTP headers. Affects script execution, style loading, image sources. Consider inline styles/scripts restrictions.
How do you implement authentication in Angular?
Authentication through JWT tokens, session management. Implement auth guards, interceptors for token handling. Secure token storage, implement refresh mechanism. Consider OAuth integration.
What is Angular's Sanitization Service?
Sanitization Service prevents XSS by sanitizing values. Handles HTML, styles, URLs, resource URLs. Use bypassSecurityTrustHtml for trusted content. Important for dynamic content rendering.
How do you handle secure data storage in Angular applications?
Secure storage using encryption, HttpOnly cookies. Consider localStorage limitations, session storage. Implement secure token management. Important for sensitive data protection.
What are security best practices for Angular routing?
Route security through guards, proper navigation. Validate route parameters, implement access control. Consider deep linking security, route resolvers. Important for navigation security.
How do you handle HTTP security headers in Angular?
Security headers through server configuration, interceptors. Implement HSTS, CSP, X-Frame-Options. Consider browser compatibility, header requirements. Important for transport security.
What is security through HTTP interceptors?
Interceptors add security headers, handle tokens. Implement authentication, request/response transformation. Consider error handling, retry logic. Important for API security.
How do you implement role-based access control (RBAC)?
RBAC through guards, directives, services. Check user roles, permissions. Implement hierarchical roles, component visibility. Important for access management.
What are secure coding practices in Angular?
Secure coding includes: input validation, output encoding, proper error handling. Avoid dangerous APIs, implement security controls. Consider secure defaults, code review.
How do you handle sensitive data transmission?
Secure transmission through HTTPS, proper encryption. Implement token-based authentication, secure headers. Consider data minimization, transport security. Important for data protection.
What is DOM-based XSS and its prevention?
DOM-based XSS occurs through client-side JavaScript. Prevent through proper sanitization, avoiding dangerous APIs. Use Angular's built-in protections, validate user input. Consider template security.
How do you implement secure file uploads?
Secure uploads through proper validation, type checking. Implement size limits, scan for malware. Consider storage location, access control. Important for upload security.
What are security considerations for forms?
Form security through validation, CSRF protection. Implement proper error handling, input sanitization. Consider client/server validation, secure submission. Important for user input.
How do you implement OAuth 2.0/OpenID Connect?
OAuth implementation through authentication libraries, proper flow. Handle token management, user sessions. Consider security best practices, implementation standards.
What is the Same-Origin Policy and its impact?
Same-Origin Policy restricts resource access between origins. Affects AJAX requests, cookies, DOM access. Configure CORS for cross-origin requests. Important for application security.
How do you handle security in service workers?
Service worker security through proper scope, HTTPS requirement. Implement secure caching, request handling. Consider update mechanism, cache poisoning prevention.
What are security considerations for WebSockets?
WebSocket security through authentication, message validation. Implement secure connection, proper error handling. Consider connection timeout, protocol security.
How do you implement secure state management?
Secure state through proper storage, access control. Implement encryption for sensitive data, clear on logout. Consider state persistence, security implications.
What are security auditing tools for Angular?
Security tools include: npm audit, OWASP ZAP, SonarQube. Regular dependency checking, vulnerability scanning. Consider automation, continuous monitoring.
How do you handle session management securely?
Secure sessions through proper timeout, token rotation. Implement session validation, concurrent session handling. Consider session fixation prevention.
What is security testing in Angular applications?
Security testing through penetration testing, vulnerability scanning. Implement security unit tests, integration tests. Consider OWASP guidelines, security requirements.
How do you secure Angular CLI production builds?
Secure builds through proper configuration, optimization. Enable production mode, implement source map protection. Consider build optimization, security flags.
What are API security best practices?
API security through proper authentication, rate limiting. Implement input validation, error handling. Consider API versioning, documentation security.
How do you handle error messages securely?
Secure error handling through proper message sanitization, logging. Implement user-friendly messages, avoid sensitive information. Consider error tracking, monitoring.
What is security hardening in Angular applications?
Security hardening through configuration, best practices. Implement security headers, proper permissions. Consider environment security, deployment practices.
How do you implement secure routing guards?
Secure guards through proper authentication, authorization checks. Implement role-based access, navigation control. Consider guard composition, reusability.
What are security considerations for PWAs?
PWA security through HTTPS requirement, secure manifests. Implement proper caching strategies, update mechanisms. Consider offline security, service worker security.
What are the different ways components can communicate in Angular?
Components communicate through: @Input/@Output decorators, services, ViewChild/ContentChild, event emitters, observables/subjects, NgRx store. Each method suitable for different scenarios based on component relationships.
How do @Input and @Output decorators work?
@Input passes data from parent to child, @Output emits events from child to parent. @Input binds property, @Output uses EventEmitter. Important for parent-child communication. Consider property changes detection.
What is ViewChild and its usage?
ViewChild accesses child component/element in template. Provides direct reference to child instance. Used for method calls, property access. Consider lifecycle hooks timing.
How do services facilitate component communication?
Services share data between unrelated components. Use observables/subjects for state management. Implement singleton services for global state. Consider dependency injection scope.
What is the role of EventEmitter?
EventEmitter emits custom events from child components. Used with @Output decorator. Supports event data passing, multiple subscribers. Consider unsubscription, memory management.
How do you implement sibling component communication?
Sibling communication through shared service, parent component mediation. Use observables/subjects for state sharing. Consider component hierarchy, data flow direction.
What is ContentChild and its use cases?
ContentChild accesses content projection elements. Used with ng-content directive. Access projected content references. Consider content initialization timing.
How do you handle component communication in large applications?
Large application communication through state management (NgRx), service layers. Implement proper data flow, component organization. Consider scalability, maintainability.
What are subjects in component communication?
Subjects are special observables for multicasting. Types: Subject, BehaviorSubject, ReplaySubject. Used in services for state sharing. Consider subscription management.
How do you implement parent-to-child method calls?
Parent-to-child method calls through ViewChild reference, @Input properties. Consider component lifecycle, method availability. Important for component interaction.
What is content projection in Angular?
Content projection (ng-content) passes content from parent to child. Supports single/multiple slots, conditional projection. Important for component reusability.
How do you handle event bubbling between components?
Event bubbling through host listeners, custom events. Control event propagation, implement handlers. Consider event capture, delegation patterns.
What are component interaction patterns?
Interaction patterns: mediator, observer, pub/sub patterns. Choose based on component relationships, data flow needs. Consider maintainability, testability.
How do you handle dynamic component communication?
Dynamic component communication through ComponentFactoryResolver, service injection. Handle component creation, destruction. Consider lifecycle management.
What is the role of change detection in component communication?
Change detection updates view based on data changes. Affects @Input property updates, event handling. Consider OnPush strategy, performance implications.
How do you implement two-way binding?
Two-way binding through [(ngModel)] or custom implementation. Combine @Input and @Output. Consider change detection, event handling. Important for form controls.
What are async pipes in component communication?
Async pipe handles observables/promises in template. Automatic subscription management, value updates. Important for reactive programming patterns.
How do you handle component state synchronization?
State synchronization through services, observables. Implement proper update mechanisms, handle race conditions. Consider state consistency, updates timing.
What are component lifecycles in communication?
Lifecycles affect communication timing (ngOnInit, ngOnChanges). Handle initialization, updates, destruction. Consider parent-child timing, change detection.
How do you handle component error communication?
Error communication through error events, error services. Implement proper error handling, user feedback. Consider error boundaries, recovery strategies.
What are component interfaces in communication?
Interfaces define component communication contracts. Specify input/output properties, methods. Important for type safety, documentation. Consider interface segregation.
How do you implement cross-module communication?
Cross-module communication through shared services, state management. Consider module boundaries, service providers. Important for modular applications.
What are best practices for component communication?
Best practices: proper encapsulation, clear interfaces, unidirectional data flow. Consider component responsibility, communication patterns. Important for maintainability.
How do you handle component property changes?
Property changes through ngOnChanges lifecycle hook, setter methods. Implement change detection, update logic. Consider simple/complex properties.
What is the role of dependency injection in communication?
Dependency injection provides services, shared instances. Manages component dependencies, service scope. Important for loosely coupled components.
How do you implement component query parameters?
Query parameters through router service, ActivatedRoute. Share state through URL parameters. Consider parameter persistence, navigation handling.
What are component decorators in communication?
Decorators (@Component, @Input, @Output) configure component behavior. Define metadata, communication interfaces. Important for component definition.
How do you handle component lazy loading communication?
Lazy loading communication through service injection, state management. Handle module loading, component initialization. Consider communication timing.
What are component communication anti-patterns?
Anti-patterns: tight coupling, excessive prop drilling, global state abuse. Avoid direct DOM manipulation, complex parent-child chains. Consider code maintainability.
What are directives in Angular and their types?
Directives are classes that modify elements. Types: Component directives (with template), Structural directives (modify DOM structure like *ngIf), Attribute directives (modify element behavior like [ngStyle]). Core building blocks of Angular.
How do you create a custom directive?
Create using @Directive decorator. Implement logic in class methods. Use ElementRef/Renderer2 for DOM manipulation. Can have inputs/outputs, host listeners. Consider selector naming, encapsulation.
What are structural directives and how do they work?
Structural directives modify DOM structure. Examples: *ngIf, *ngFor, *ngSwitch. Use microsyntax with asterisk (*). Create template views, handle context. Important for dynamic content.
What is the difference between pure and impure pipes?
Pure pipes execute only on pure changes (primitive/reference). Impure pipes execute on every change detection. Pure pipes better for performance. Impure needed for dynamic transformations.
How do you create a custom pipe?
Create using @Pipe decorator. Implement PipeTransform interface. Define transform method for conversion logic. Can accept multiple arguments. Consider pure/impure setting.
What are attribute directives and their use cases?
Attribute directives change element appearance/behavior. Examples: ngStyle, ngClass. Can respond to user events, modify element properties. Used for dynamic styling, behavior modification.
How do you handle events in custom directives?
Events handled through @HostListener decorator. Respond to DOM events, custom events. Can access event data, element properties. Consider event propagation, prevention.
What are the built-in pipes in Angular?
Built-in pipes: DatePipe, UpperCasePipe, LowerCasePipe, CurrencyPipe, DecimalPipe, PercentPipe, AsyncPipe, JsonPipe. Each serves specific transformation need. Consider localization support.
How do you implement directive composition?
Directive composition through multiple directives on element. Handle directive interaction, priority. Consider order of execution, conflicts. Important for complex behaviors.
What is async pipe and its benefits?
AsyncPipe unwraps observable/promise values. Automatically handles subscription/unsubscription. Updates view on new values. Important for reactive programming, memory management.
How do you implement custom structural directives?
Custom structural directives use TemplateRef, ViewContainerRef. Create/destroy views programmatically. Handle context binding, view manipulation. Consider microsyntax support.
What are directive lifecycle hooks?
Directive lifecycles: ngOnInit, ngOnDestroy, ngOnChanges, etc. Handle initialization, changes, cleanup. Consider timing, dependency availability. Important for proper resource management.
How do you handle pipe parameters?
Pipe parameters passed after colon in template. Multiple parameters separated by colons. Access in transform method. Consider optional parameters, default values.
What are host bindings in directives?
Host bindings modify host element properties/attributes. Use @HostBinding decorator. Bind to element properties, classes, styles. Consider property naming, updates.
How do you implement pipe chaining?
Pipe chaining connects multiple pipes sequentially. Order matters for transformation. Consider data type compatibility, performance. Use for complex transformations.
What are exported directives?
Exported directives available for template reference. Use exportAs property. Access directive methods/properties in template. Important for directive interaction.
How do you handle directive dependencies?
Directive dependencies injected through constructor. Access services, other directives. Consider dependency scope, availability. Important for directive functionality.
What are the best practices for custom pipes?
Best practices: pure by default, handle null/undefined, proper error handling. Consider performance impact, reusability. Document parameters, behavior.
How do you test directives and pipes?
Testing through TestBed configuration, component creation. Test directive behavior, pipe transformations. Consider different scenarios, edge cases. Important for reliability.
What is template context in structural directives?
Template context provides data to template. Access through let syntax. Define custom context properties. Important for dynamic content, loops.
How do you handle dynamic pipes?
Dynamic pipes selected at runtime. Use pipe binding syntax. Consider pipe availability, performance. Important for flexible transformations.
What are directive queries?
Directive queries access other directives. Use ContentChild/ContentChildren, ViewChild/ViewChildren. Access child directives, elements. Consider timing, availability.
How do you handle pipe errors?
Pipe errors handled through error handling, default values. Consider null checks, type validation. Provide meaningful error messages. Important for robust applications.
What are directive selectors patterns?
Selector patterns: element, attribute, class selectors. Define directive application scope. Consider naming conventions, specificity. Important for proper directive usage.
How do you implement internationalization in pipes?
i18n in pipes through locale services, formatting options. Support different formats, languages. Consider cultural differences, formats. Important for global applications.
What are common directive patterns?
Common patterns: decorator pattern, adapter pattern, composite pattern. Apply based on use case. Consider reusability, maintainability. Important for scalable applications.
How do you optimize directive performance?
Optimization through proper change detection, minimal DOM manipulation. Use OnPush strategy when possible. Consider event binding, updates frequency. Important for application performance.
What are directive communication patterns?
Communication through inputs/outputs, services, events. Handle parent-child interaction, sibling communication. Consider component hierarchy, data flow. Important for complex directives.
How do you handle directive conflicts?
Conflicts resolved through priority, specific selectors. Handle multiple directives, compatibility. Consider directive composition, interaction. Important for complex applications.
What are the key principles of Angular architecture?
Key principles include: Modularity (feature modules), Component-based architecture, Dependency Injection, Separation of Concerns, Single Responsibility. Focus on maintainability, scalability, and reusability. Consider proper layer separation.
How do you structure a large Angular application?
Structure using feature modules, core/shared modules, lazy loading. Implement proper folder organization, naming conventions. Consider scalability, maintainability. Follow LIFT principle (Locatable, Isolated, Focused, Testable).
What is the role of Core Module in Angular?
Core Module contains singleton services, one-time imported components. Houses app-wide services, guards, interceptors. Should be imported only in AppModule. Ensures single instance of services.
What are feature modules and their importance?
Feature modules organize related components, services, pipes. Support lazy loading, encapsulation. Improve maintainability, testing. Consider domain boundaries, functionality grouping.
How do you implement smart and presentational components?
Smart components handle business logic, data. Presentational components focus on UI, receive data via inputs. Promotes reusability, separation of concerns. Consider component responsibility division.
What is the Shared Module pattern?
Shared Module contains common components, pipes, directives. Imported by feature modules. Avoids code duplication, promotes reuse. Consider module size, import frequency.
How do you implement scalable state management?
State management through services (small apps) or NgRx/other state libraries (large apps). Consider data flow, state access patterns. Implement proper immutability, change detection strategies.
What are the best practices for service architecture?
Service architecture: proper separation, single responsibility, injectable services. Consider service scope, dependency injection. Implement proper error handling, logging.
How do you implement domain-driven design in Angular?
DDD through feature modules, domain services, entities. Organize by business domains. Consider bounded contexts, domain logic separation. Important for complex business applications.
What are the patterns for component communication?
Communication patterns: Input/Output, Services, State Management, Event Bus. Choose based on component relationship, data flow needs. Consider component coupling, maintainability.
How do you implement application-wide error handling?
Error handling through ErrorHandler service, HTTP interceptors. Implement centralized error logging, user feedback. Consider different error types, recovery strategies.
What are the best practices for API integration?
API integration: service layer abstraction, typed interfaces, proper error handling. Implement caching, retry strategies. Consider API versioning, security.
How do you implement micro-frontend architecture?
Micro-frontends through Module Federation, Custom Elements. Handle inter-app communication, shared dependencies. Consider deployment strategy, team organization.
What are the patterns for form management?
Form patterns: Template-driven vs Reactive forms, form builders, validation services. Consider form complexity, validation requirements. Implement proper error handling, user feedback.
How do you implement security best practices?
Security practices: XSS prevention, CSRF protection, secure authentication. Implement proper authorization, input validation. Consider security headers, secure configuration.
What are the patterns for route management?
Route patterns: feature-based routing, guard protection, resolvers. Implement proper navigation, data preloading. Consider lazy loading, route parameters.
How do you implement performance optimization?
Performance optimization: lazy loading, change detection strategy, bundle optimization. Implement proper caching, virtual scrolling. Consider loading strategies, performance metrics.
What are the best practices for testing architecture?
Testing architecture: unit tests, integration tests, e2e tests. Implement proper test organization, coverage. Consider test pyramid, testing strategies.
How do you implement internationalization architecture?
i18n architecture: translation files, language services, locale handling. Implement proper text extraction, runtime translation. Consider cultural differences, formatting.
What are the patterns for authentication/authorization?
Auth patterns: JWT handling, guard protection, role-based access. Implement secure token storage, refresh mechanisms. Consider session management, security.
How do you implement reusable component libraries?
Component libraries: shared styles, documentation, versioning. Implement proper encapsulation, API design. Consider reusability, maintainability.
What are the best practices for dependency management?
Dependency management: proper versioning, package organization, update strategy. Implement dependency injection, module organization. Consider bundle size, compatibility.
How do you implement logging architecture?
Logging architecture: centralized logging, error tracking, monitoring. Implement proper log levels, storage strategy. Consider privacy, performance impact.
What are the patterns for offline support?
Offline patterns: service workers, local storage, sync mechanisms. Implement proper caching, data persistence. Consider offline-first approach, sync conflicts.
How do you implement CI/CD best practices?
CI/CD practices: automated testing, build optimization, deployment strategy. Implement proper environment configuration, versioning. Consider deployment automation, monitoring.
What are the best practices for code organization?
Code organization: proper folder structure, naming conventions, module organization. Implement feature-based structure, shared code. Consider scalability, maintainability.
How do you implement accessibility best practices?
Accessibility practices: ARIA labels, keyboard navigation, screen reader support. Implement proper semantic markup, focus management. Consider WCAG guidelines, testing.
What are the patterns for real-time updates?
Real-time patterns: WebSocket integration, polling strategies, state updates. Implement proper connection management, error handling. Consider scalability, performance.
How do you implement progressive enhancement?
Progressive enhancement: feature detection, fallback strategies, graceful degradation. Implement proper browser support, feature flags. Consider user experience, compatibility.
What is the global error handling mechanism in Angular?
Global error handling through ErrorHandler class. Override handleError method for custom handling. Catches all unhandled errors. Implement logging, user notification, error reporting.
How do you handle HTTP errors in Angular?
HTTP errors handled through interceptors, catchError operator. Implement retry logic, error transformation. Use error handling services. Consider different error types, user feedback.
What are error boundaries in Angular?
Error boundaries through component error handlers, ngOnError hook. Catch and handle rendering errors. Implement fallback UI, error recovery. Consider component hierarchy.
How do you implement form validation error handling?
Form errors through validators, error states. Display validation messages, highlight errors. Implement custom validators, async validation. Consider user experience, feedback timing.
What are RxJS error handling operators?
RxJS operators: catchError, retry, retryWhen, throwError. Handle stream errors, implement recovery logic. Consider error transformation, retry strategies.
How do you implement error logging services?
Error logging through centralized service. Log error details, stack traces. Implement remote logging, error tracking. Consider privacy, performance impact.
What are the best practices for error handling?
Best practices: centralized handling, proper error types, user feedback. Implement logging, monitoring. Consider error recovery, graceful degradation.
How do you handle async operation errors?
Async errors through Promise catch, Observable error handling. Implement proper error propagation, recovery. Consider loading states, timeout handling.
What are error notification strategies?
Error notifications through toasts, alerts, error pages. Implement user-friendly messages, action options. Consider error severity, context-appropriate feedback.
How do you handle route navigation errors?
Navigation errors through Router error events, guards. Implement redirection, error pages. Consider route parameters, navigation history.
What are error recovery patterns?
Recovery patterns: retry logic, fallback options, graceful degradation. Implement automatic recovery, manual intervention. Consider user experience, data integrity.
How do you implement error tracking?
Error tracking through monitoring services, custom tracking. Implement error aggregation, analysis. Consider error patterns, impact assessment.
What are error prevention strategies?
Prevention strategies: input validation, type checking, defensive programming. Implement proper error boundaries, testing. Consider edge cases, error scenarios.
How do you handle memory leaks?
Memory leak prevention through proper unsubscription, cleanup. Implement resource management, leak detection. Consider component lifecycle, subscription handling.
What are error monitoring tools?
Monitoring tools: Sentry, LogRocket, custom solutions. Implement error tracking, performance monitoring. Consider tool integration, configuration.
How do you handle third-party library errors?
Library errors through error wrapping, custom handlers. Implement proper integration, error transformation. Consider library updates, compatibility issues.
What are error testing strategies?
Error testing through unit tests, integration tests. Test error scenarios, recovery logic. Consider error simulation, boundary testing.
How do you handle production errors?
Production errors through logging, monitoring, alerts. Implement error reporting, analysis. Consider environment differences, security implications.
What are error serialization strategies?
Error serialization for logging, transmission. Implement proper error format, data extraction. Consider sensitive information, error context.
How do you handle offline errors?
Offline errors through connection checking, retry logic. Implement offline storage, sync mechanisms. Consider network conditions, data persistence.
What are error boundary patterns?
Boundary patterns: component-level, route-level, app-level boundaries. Implement proper error isolation, recovery. Consider error propagation, UI feedback.
How do you handle state management errors?
State errors through error actions, error states. Implement state recovery, rollback mechanisms. Consider state consistency, error propagation.
What are error handling anti-patterns?
Anti-patterns: swallowing errors, generic error messages, missing logging. Avoid broad catch blocks, silent failures. Consider proper error handling practices.
How do you handle initialization errors?
Initialization errors through APP_INITIALIZER, bootstrap handling. Implement proper startup checks, fallbacks. Consider application requirements, dependencies.
What are error reporting best practices?
Reporting practices: proper error format, context inclusion, aggregation. Implement error categorization, priority handling. Consider privacy, compliance requirements.
How do you handle security-related errors?
Security errors through proper validation, authorization checks. Implement secure error messages, logging. Consider sensitive information, attack vectors.
What are error documentation practices?
Documentation practices: error codes, handling procedures, recovery steps. Implement proper error guides, troubleshooting docs. Consider user/developer documentation.
How do you handle performance-related errors?
Performance errors through monitoring, optimization. Implement performance boundaries, error tracking. Consider resource usage, user experience impact.
What are error handling metrics?
Error metrics: error rates, recovery times, impact assessment. Implement metric collection, analysis. Consider monitoring, alerting thresholds.
How do you handle dependency injection errors?
DI errors through proper provider configuration, error catching. Implement fallback providers, error messages. Consider circular dependencies, missing providers.
What are the essential debugging tools for Angular applications?
Essential tools include: Angular DevTools, Chrome DevTools, Source Maps, Augury (legacy), console methods, debugger statement. VS Code debugging extensions. Browser developer tools for network, performance analysis.
How do you debug change detection issues?
Debug change detection using: enableDebugTools(), profiler, zones visualization. Check for unnecessary triggers, performance impacts. Analyze component update cycles, implement proper change detection strategy.
What techniques are used for debugging memory leaks?
Debug memory leaks using: Chrome Memory profiler, heap snapshots, timeline recording. Check subscription cleanup, component destruction. Monitor memory usage patterns, implement proper unsubscribe patterns.
How do you debug routing issues?
Debug routing through Router events logging, Router state inspection. Check guard conditions, route configurations. Analyze navigation lifecycle, implement proper route tracing.
What are common performance debugging techniques?
Performance debugging using: Chrome Performance tools, Angular profiler, network tab. Analyze bundle sizes, rendering times, bottlenecks. Monitor CPU usage, implement performance optimizations.
How do you debug HTTP requests?
Debug HTTP through Network tab, HttpInterceptors logging. Monitor request/response cycles, analyze headers/payloads. Check error responses, implement proper request tracking.
What strategies are used for debugging production issues?
Production debugging through: error logging services, source maps, monitoring tools. Implement proper error tracking, user feedback collection. Analyze production logs, error patterns.
How do you debug dependency injection issues?
Debug DI through provider configuration checks, injection tree analysis. Verify service providers, scope issues. Check circular dependencies, implement proper provider debugging.
What methods are used for debugging template issues?
Template debugging through: browser inspection, Angular DevTools. Check bindings, expressions, structural directives. Analyze template syntax, implement proper debugging statements.
How do you debug state management issues?
State debugging through: Redux DevTools, state logging, action tracing. Monitor state changes, action effects. Analyze state mutations, implement proper state tracking.
What techniques are used for debugging async operations?
Async debugging through: async/await breakpoints, observable debugging. Monitor promise chains, subscription flows. Analyze async timing issues, implement proper async tracking.
How do you debug form validation issues?
Form debugging through form state inspection, validation checks. Monitor form controls, error states. Analyze validation rules, implement proper form debugging.
What are common build issues and their solutions?
Build issues debugging through: build logs, configuration checks. Verify dependencies, version conflicts. Analyze build errors, implement proper build debugging.
How do you debug lazy loading issues?
Lazy loading debugging through: network monitoring, chunk loading analysis. Check module configurations, route setup. Analyze loading patterns, implement proper chunk tracking.
What strategies are used for debugging component interactions?
Component interaction debugging through: input/output tracking, service communication monitoring. Check component hierarchy, event propagation. Analyze component communication patterns.
How do you debug AOT compilation issues?
AOT debugging through: compilation errors analysis, template checking. Verify syntax compatibility, type checking. Analyze compilation process, implement proper AOT debugging.
What methods are used for debugging security issues?
Security debugging through: CORS analysis, XSS checks, authentication flow verification. Monitor security headers, implement proper security debugging.
How do you debug SSR (Server-Side Rendering) issues?
SSR debugging through: server logs, hydration checks. Verify platform-specific code, state transfer. Analyze rendering process, implement proper SSR debugging.
What techniques are used for debugging zone.js issues?
Zone.js debugging through: zone hooks monitoring, async operation tracking. Check zone contexts, patched methods. Analyze zone behavior, implement proper zone debugging.
How do you debug internationalization issues?
i18n debugging through: translation key checks, locale loading verification. Monitor translation process, cultural formatting. Analyze localization issues, implement proper i18n debugging.
What are common optimization debugging techniques?
Optimization debugging through: bundle analysis, performance profiling. Check optimization configurations, tree-shaking. Analyze build optimization, implement proper performance debugging.
How do you debug PWA (Progressive Web App) issues?
PWA debugging through: service worker inspection, cache analysis. Verify manifest configuration, offline behavior. Analyze PWA features, implement proper PWA debugging.
What strategies are used for debugging test failures?
Test debugging through: test runner inspection, assertion analysis. Check test setup, mock configurations. Analyze test environment, implement proper test debugging.
How do you debug accessibility issues?
Accessibility debugging through: ARIA validation, screen reader testing. Check semantic markup, keyboard navigation. Analyze accessibility requirements, implement proper a11y debugging.
What techniques are used for debugging CSS issues?
CSS debugging through: style inspection, layout analysis. Check style encapsulation, view encapsulation. Analyze styling issues, implement proper CSS debugging.
How do you debug WebSocket connections?
WebSocket debugging through: connection state monitoring, message logging. Verify connection lifecycle, error handling. Analyze real-time communication, implement proper WebSocket debugging.
What methods are used for debugging third-party library integration?
Library debugging through: integration verification, API usage analysis. Check compatibility issues, version conflicts. Analyze library behavior, implement proper integration debugging.
How do you debug environmental configuration issues?
Environment debugging through: configuration file analysis, variable checking. Verify environment setup, build configurations. Analyze environment-specific issues, implement proper config debugging.
What are common browser compatibility debugging techniques?
Browser compatibility debugging through: cross-browser testing, feature detection. Check polyfills, browser-specific issues. Analyze compatibility requirements, implement proper browser debugging.
What is the Angular CLI build process and its key features?
Angular CLI build process includes: compilation, bundling, minification, tree-shaking. Uses webpack under the hood. Key features: production optimization, source maps generation, differential loading. Configured through angular.json.
How do you configure different environments in Angular?
Environments configured through environment.ts files. Create environment-specific files, use fileReplacements in angular.json. Configure variables per environment. Important for different deployment scenarios.
What is Ahead-of-Time (AOT) compilation?
AOT compiles templates during build process. Benefits: faster rendering, smaller file size, better security. Default in production builds. Catches template errors during build time.
How do you implement continuous integration/deployment (CI/CD)?
CI/CD implementation through pipelines (Jenkins, GitLab CI, etc.). Include build, test, deploy stages. Configure environment variables, deployment targets. Consider automated testing, versioning.
What are build optimization techniques?
Optimization techniques: bundle splitting, lazy loading, tree shaking, compression. Configure production build flags, performance budgets. Consider source map generation, cache busting.
How do you handle deployment configurations?
Deployment configurations through environment files, runtime configuration. Handle API endpoints, feature flags, third-party keys. Consider security, configuration management.
What is the role of webpack in Angular builds?
Webpack handles module bundling, asset management, dependency resolution. Configures loaders, plugins for build process. Customizable through custom webpack configuration. Important for build optimization.
How do you implement versioning strategies?
Versioning through semantic versioning, automated version bumping. Configure version management in package.json, git tags. Consider changelog generation, release notes.
What are deployment strategies for Angular applications?
Deployment strategies: blue-green deployment, canary releases, rolling updates. Consider zero-downtime deployment, rollback capabilities. Implement proper monitoring, health checks.
How do you implement Docker containerization?
Docker implementation through multi-stage builds, optimized images. Configure Nginx for serving, environment variables. Consider container orchestration, scaling strategies.
What are production build considerations?
Production considerations: optimization flags, environment configuration, security measures. Enable production mode, implement proper error handling. Consider performance, monitoring setup.
How do you handle assets in production builds?
Asset handling through angular.json configuration, CDN integration. Optimize images, manage static files. Consider caching strategies, asset versioning.
What is Server-Side Rendering (SSR) deployment?
SSR deployment using Angular Universal, server configuration. Handle server-side execution, state transfer. Consider SEO requirements, performance implications.
How do you implement PWA deployment?
PWA deployment through service worker configuration, manifest setup. Handle offline capabilities, caching strategies. Consider update flow, notification handling.
What are deployment automation tools?
Automation tools: Jenkins, GitLab CI, GitHub Actions, Azure DevOps. Configure build pipelines, deployment scripts. Consider integration testing, automated releases.
How do you handle dependency management in production?
Dependency management through package-lock.json, npm/yarn. Handle version conflicts, security updates. Consider dependency auditing, update strategies.
What are build artifacts management strategies?
Artifact management through artifact repositories, versioning system. Handle storage, distribution of builds. Consider cleanup policies, retention rules.
How do you implement rolling updates?
Rolling updates through deployment orchestration, version management. Handle traffic routing, health checks. Consider zero-downtime deployment, rollback procedures.
What are monitoring strategies post-deployment?
Monitoring through logging services, performance tracking. Implement error tracking, user analytics. Consider alerting systems, incident response.
How do you handle configuration management?
Configuration management through environment files, runtime config. Implement secure storage, access control. Consider configuration versioning, audit trail.
What is the role of build optimization flags?
Optimization flags control build process features. Include production mode, bundling options, optimization levels. Consider performance impact, debugging capabilities.
How do you implement multi-environment deployment?
Multi-environment through environment-specific configurations, deployment pipelines. Handle different settings, API endpoints. Consider environment isolation, access control.
What are deployment security considerations?
Security considerations: HTTPS setup, CSP configuration, secure headers. Implement access controls, security scanning. Consider vulnerability assessment, compliance requirements.
How do you handle deployment rollbacks?
Rollbacks through version control, deployment history. Implement automated rollback procedures. Consider data consistency, dependency compatibility.
What are build performance optimization techniques?
Build performance through caching, parallel processing, incremental builds. Optimize build configuration, dependency management. Consider CI/CD pipeline efficiency.
How do you implement feature flags in deployment?
Feature flags through configuration management, runtime toggles. Handle feature enabling/disabling, A/B testing. Consider flag cleanup, documentation.
What are deployment testing strategies?
Deployment testing through smoke tests, integration tests. Implement automated validation, environment verification. Consider test coverage, failure scenarios.
How do you handle database migrations in deployment?
Database migrations through versioning, rollback support. Implement migration scripts, data validation. Consider zero-downtime updates, data integrity.
What are deployment documentation practices?
Documentation practices: deployment procedures, configuration guides, troubleshooting steps. Maintain version history, change logs. Consider knowledge transfer, maintenance.
How do you implement cache management in deployment?
Cache management through versioning, cache busting strategies. Handle browser caching, CDN configuration. Consider cache invalidation, performance impact.
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