Q: What is the async pipe and why is it useful?

**Target Audience:** Developers who have written | async in a template and want to know exactly what it does — assumes basic Observables, explains everything else. **Difficulty:** Easy to Medium > **How to read this doc:** Plain language first, then 📌 Interview term: callouts. The behaviour below was produced on Angular 22.2.3: templates compiled with ngc (strict templates), run in jsdom, and subscriptions counted with instrumented Observables. The "insid

Question 1

What is Angular and how does it differ from AngularJS?

Accepted Answer

**Target Audience:** Anyone preparing for an Angular interview — assumes basic JavaScript, no Angular or AngularJS required. **Difficulty:** Easy > **How to read this doc:** Ideas are explained in plain language first, then tagged with 📌 Interview term: so you also learn the words an interviewer listens for. The output in section 5 was produced by compiling and running the example on Angular 22.2.3, and the default-behaviour claims in section 6 were read from the Angular 22.2.3 pa

Question 2

What are standalone components?

Accepted Answer

**Target Audience:** Developers preparing for an Angular interview who know what a component is and have seen, or heard of, NgModules. **Difficulty:** Easy > **How to read this doc:** Plain language first, then 📌 Interview term: callouts. Everything under a "Verified" heading was compiled with ngc on Angular 22.2.3 and run; the lazy-loading log in section 5 came from a real provideRouter setup. ## 1. Why This Even Matters — A Story First Picture packing

Question 3

What is the APP_INITIALIZER token and how is it used to load configuration at startup?

Accepted Answer

**Target Audience:** Developers wiring up real deployments, where configuration has to be known before the app can do anything useful. **Difficulty:** Medium > **How to read this doc:** Ideas are explained in plain language first, then tagged with 📌 Interview term: so you also learn the words an interviewer listens for. The timing logs in section 5 were printed by the example booting on Angular 22.2.3 (with a fake HTTP backend, since no network is involved), and the deprecation fa

Question 4

How do functional interceptors work with provideHttpClient()?

Accepted Answer

**Target Audience:** Developers who can already write a basic interceptor and want to understand the chain well enough to debug ordering problems. **Difficulty:** Medium > **How to read this doc:** Plain language first, then 📌 Interview term: callouts. The internals described here were read from the installed @angular/common 22.2.3 source, and every ordering claim was produced by running instrumented interceptors (compiled with ngc, booted in jsdom with a

Question 5

How does catchError work in RxJS, and how do you return a fallback value?

Accepted Answer

**Target Audience:** Angular developers handling HTTP failures in RxJS pipelines, especially inside search boxes, effects and other long-lived streams. **Difficulty:** Medium > **How to read this doc:** Ideas are explained in plain language first, then tagged with 📌 Interview term: so you also learn the words an interviewer listens for. Every behaviour in sections 3 to 6 was produced by running RxJS 7.8.2, and the component in section 7 was compiled and clicked through on Angular

Question 6

What is the role of NgRx Effects, and why do we separate side effects from reducers?

Accepted Answer

**Target Audience:** Angular developers who know the basics of the NgRx store (actions, reducers, selectors) and want to understand where HTTP calls and other side effects belong. **Difficulty:** Medium to Hard > **How to read this doc:** Ideas are explained in plain language first, then tagged with 📌 Interview term: so you also learn the words an interviewer listens for. The action log in section 5, the error-handling run in section 6 and the effect test in section 7 were produce

Question 7

How do you mock services in Angular unit tests using Jasmine/Jest spies?

Accepted Answer

**Target Audience:** Developers writing component and service tests who want to isolate a unit from its dependencies. **Difficulty:** Easy to Medium > **How to read this doc:** Plain language first, then 📌 Interview term: callouts. The Vitest spec in the example was run with Angular CLI 22.2.3 (ng test --watch=false, Vitest 5, zoneless). The Jasmine spy behaviour was run in plain Jasmine 5.13 under Node, without Angular, to check the syntax and defaults; the Jest synt

Question 8

What is the async pipe and why is it useful?

Accepted Answer

**Target Audience:** Developers who have written | async in a template and want to know exactly what it does — assumes basic Observables, explains everything else. **Difficulty:** Easy to Medium > **How to read this doc:** Plain language first, then 📌 Interview term: callouts. The behaviour below was produced on Angular 22.2.3: templates compiled with ngc (strict templates), run in jsdom, and subscriptions counted with instrumented Observables. The "insid

Question 9

How do toSignal() and toObservable() bridge Signals and RxJS?

Accepted Answer

**Target Audience:** Angular developers who use both signals and RxJS and want to know exactly what crosses the bridge — no prior interop knowledge needed. **Difficulty:** Medium > **How to read this doc:** Plain language first, then 📌 Interview term: callouts. The emission orders below were produced on Angular 22.2.3 (AOT with ngc, and the playground JIT mode) in jsdom, and the "how it works inside" section is read from the 22.2.3 @angular/core/rxjs-interop

Question 10

How do you handle errors and retries globally with interceptors?

Accepted Answer

**Target Audience:** Developers who know the basics of interceptors and RxJS and want a production-grade global error and retry strategy. **Difficulty:** Medium to Hard > **How to read this doc:** Plain language first, then 📌 Interview term: callouts. Every attempt count, ordering result and test outcome below was produced by running the code on Angular 22.2.3 and RxJS 7.8.2 (compiled with ngc, booted in jsdom with an exported appConfig, a fake backend in

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Easy

What is Angular and how does it differ from AngularJS?

What are standalone components?

Medium

What is the APP_INITIALIZER token and how is it used to load configuration at startup?

How do functional interceptors work with provideHttpClient()?

How does catchError work in RxJS, and how do you return a fallback value?

What is the role of NgRx Effects, and why do we separate side effects from reducers?

How do you mock services in Angular unit tests using Jasmine/Jest spies?

What is the async pipe and why is it useful?

How do toSignal() and toObservable() bridge Signals and RxJS?

How do you handle errors and retries globally with interceptors?

Hard

What are security vulnerabilities in Angular apps, and how does DomSanitizer prevent XSS?

Signals signal()/computed()/effect() vs RxJS — when do you use which in Angular 18+?

What is an InjectionToken?

What is Angular Universal / SSR?

What is NgRx?

Explain the shareReplay operator in RxJS and how it prevents duplicate HTTP requests.

What is the difference between switchMap, mergeMap, concatMap, and exhaustMap?

What is the difference between forkJoin, zip, combineLatest, and withLatestFrom?