Q: What is ngTemplateOutlet?

**Target Audience:** Developers who know what an ng-template is and want to render one on demand, pass it data, or hand it to a reusable component. **Difficulty:** Medium > **How to read this doc:** Plain language first, then 📌 Interview term: callouts. View-creation logs, rendered output and type-checking behaviour below were produced on Angular 22.2.3 by compiling with ngc (strict templates) and running in jsdom; the API descriptions were read from the

Q: What is an HTTP interceptor?

**Target Audience:** Developers who call APIs with HttpClient and want cross-cutting behaviour in one place — assumes you know what an Observable is (see [Observables vs Promises](/interview-question/what-is-the-difference-between-observables-and-promises)). **Difficulty:** Easy to Medium > **How to read this doc:** Plain language first, then 📌 Interview term: callouts. The order logs in sections 5 and 6 were printed by the compiled examples (Angular 22.2.3, ngc

Question 1

What does the Angular CLI provide?

Accepted Answer

**Target Audience:** Anyone preparing for an Angular interview — no Angular experience needed. **Difficulty:** Easy > **How to read this doc:** Plain language first, then 📌 Interview term: callouts. Everything under "Verified" was produced by running Angular CLI 22.2.3 in a sandbox: ng new, ng generate --dry-run, ng serve, ng build, ng test and ng lint, with the real output quoted. ng add an

Question 2

inject() vs constructor injection — when should you use each?

Accepted Answer

**Target Audience:** Developers and tech leads choosing a team convention, and candidates asked "which do you prefer and why?". **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. This page is the *decision guide*. What each style compiles to, the injection-context rules and the inheritance mechanics are in the sibling question [constructor-based D

Question 3

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 4

What is ngTemplateOutlet?

Accepted Answer

**Target Audience:** Developers who know what an ng-template is and want to render one on demand, pass it data, or hand it to a reusable component. **Difficulty:** Medium > **How to read this doc:** Plain language first, then 📌 Interview term: callouts. View-creation logs, rendered output and type-checking behaviour below were produced on Angular 22.2.3 by compiling with ngc (strict templates) and running in jsdom; the API descriptions were read from the

Question 5

How does Dependency Injection work in Angular?

Accepted Answer

**Target Audience:** Developers new to Angular, or who use services daily without knowing what builds them. Assumes TypeScript classes; no DI background needed. **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 output block below was produced by compiling and running the code on Angular 22.2.3; the injector chain and error messages were pri

Question 6

What is a service and why use it?

Accepted Answer

**Target Audience:** Beginners who have built a few components and are starting to duplicate logic between them. **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; the @Service() facts come from the 22.2.3 typings, the compiler and the CLI 22.2.

Question 7

What is an HTTP interceptor?

Accepted Answer

**Target Audience:** Developers who call APIs with HttpClient and want cross-cutting behaviour in one place — assumes you know what an Observable is (see [Observables vs Promises](/interview-question/what-is-the-difference-between-observables-and-promises)). **Difficulty:** Easy to Medium > **How to read this doc:** Plain language first, then 📌 Interview term: callouts. The order logs in sections 5 and 6 were printed by the compiled examples (Angular 22.2.3, ngc

Question 8

What is the purpose of the KeyValueDiffers and IterableDiffers services?

Accepted Answer

**Target Audience:** Developers who know inputs and lifecycle hooks and have hit "my child component did not notice the change" — no knowledge of Angular internals needed. **Difficulty:** Hard > **How to read this doc:** Plain language first, then 📌 Interview term: callouts with the vocabulary an interviewer expects. Every change report and error message below was produced by compiling and running the code on Angular 22.2.3; which built-ins use differs was read from the 22.2.3

Question 9

What is the effect() function in Angular Signals, and when should you NOT use it?

Accepted Answer

**Target Audience:** Developers who know what a signal is and want to use effect() correctly — assumes basic Angular components, explains everything else. **Difficulty:** Medium > **How to read this doc:** Plain language first, then 📌 Interview term: callouts with the words an interviewer listens for. Every ordering and output block below was produced by compiling the code with ngc (strict templates) on Angular 22.2.3 and running it in jsdom; API status c

Question 10

What are the differences between State Management libraries in Angular?

Accepted Answer

**Target Audience:** Angular developers and tech leads choosing a state-management approach for a new or growing app. **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 two implementations in section 6 were compiled and run on Angular 22.2.3 with @ngrx/signals 22.0.1, the API-stability claims were read from the installed package typing

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