Angular Interview Questions for Indian Developers 2026

Angular is a full-featured, opinionated framework from Google. Core concepts: Component (TypeScript class + HTML template + CSS), Directive (structural ngIf/ngFor change DOM structure; attribute ngClass/ngStyle change appearance), Service (injectable TypeScript class for shared logic: singleton by default in root injector), Module (NgModule: container for components, directives, pipes, services; Angular 14+ supports standalone components), Pipe (transforms template values: DatePipe, CurrencyPipe, custom pipes). Dependency Injection is Angular's mechanism for providing services to components without tight coupling.

RxJS is deeply integrated into Angular: used for HTTP, forms, routing, and async operations. Observable: a stream that can emit 0 or more values over time. Always unsubscribe to prevent memory leaks (takeUntil, async pipe, or unsubscribe in ngOnDestroy). Subject: Observable that also acts as Observer. BehaviorSubject: emits the last value to new subscribers: most used for simple Angular state management. Key operators: map, filter, switchMap (cancel previous inner Observable on new emission), mergeMap (maintain concurrent Observables), catchError, forkJoin, combineLatest. The async pipe automatically subscribes and unsubscribes in templates.

Template-driven forms: use directives in HTML (ngModel, ngForm). Simpler, less testable. Reactive forms: form structure defined in TypeScript (FormBuilder, FormGroup, FormControl). More explicit, more testable, better for complex and dynamic forms: the recommended approach. Validators: built-in (Validators.required, Validators.email) and custom (synchronous and asynchronous). Async validators: useful for server-side validation (username taken check). Interview question: When would you use template-driven vs reactive forms? Template-driven: simple static forms. Reactive: complex, dynamic, heavily validated forms.

Modern Angular features increasingly tested in 2026: Standalone components (Angular 14+, default in Angular 17): no NgModule required. Angular Signals (Angular 16+): reactive primitive for fine-grained change detection: the Angular answer to React hooks, replaces much RxJS for local state. Control flow syntax (Angular 17+): @if, @for, @switch replace ngIf, ngFor: cleaner syntax and better performance. Deferred loading (@defer in Angular 17): lazy-load components declaratively. OnPush change detection: only re-render when inputs change: critical performance technique for large apps.