Question 1

Explain the difference between FormGroup.patchValue() and FormGroup.setValue().

Accepted Answer

**Target Audience:** Developers who have built at least one reactive form and want to know exactly how its update methods behave. **Difficulty:** Easy to Medium > **How to read this doc:** Plain language first, then 📌 Interview term: callouts. Every error message and value quoted below was printed by running the code on Angular 22.2.3, either in the runnable example (compiled with ngc, booted in jsdom and clicked through by a driver) or in small scripts against

Question 2

What are components and modules in Angular?

Accepted Answer

**Target Audience:** Anyone preparing for an Angular interview — assumes basic TypeScript classes, no Angular required. **Difficulty:** Easy > **How to read this doc:** Plain language first, then 📌 Interview term: callouts with the vocabulary an interviewer expects. Every output and error message quoted below was produced by compiling the code with ngc (strict templates) on Angular 22.2.3 and running it. ## 1. Why This Even Matters — A Story First Think of a restaur

Question 3

What is the purpose of ngOnChanges and how does it capture changes in @Input properties?

Accepted Answer

**Target Audience:** Developers preparing for an Angular interview who have written a component with an @Input and want to know exactly when Angular tells the component that the input changed. **Difficulty:** Medium > **How to read this doc:** Plain language first, then 📌 Interview term: callouts with the vocabulary an interviewer expects. Everything under a "Verified" heading was compiled with ngc (strict templates) on Angular 22.2.3 and run; the output

Question 4

How do child components emit events to parents?

Accepted Answer

**Target Audience:** Anyone preparing for an Angular interview who knows what a component and an input are. **Difficulty:** Easy > **How to read this doc:** Plain language first, then 📌 Interview term: callouts. The call order in section 4 and the bubbling test in section 5 were produced by compiling the examples with ngc on Angular 22.2.3 and clicking through them in jsdom. ## 1. Why This Even Matters — A Story First A child at a school play does not walk into the

Question 5

What are the types of data binding in Angular?

Accepted Answer

**Target Audience:** Anyone preparing for an Angular interview — assumes HTML and a little TypeScript. **Difficulty:** Easy > **How to read this doc:** Plain language first, then 📌 Interview term: callouts. The outputs, compiler errors and the generated instructions quoted below all came from compiling the code with ngc on Angular 22.2.3 and running it in jsdom. ## 1. Why This Even Matters — A Story First Think of a component as a shop and the template as its shop w

Question 6

What is a route resolver and when is it useful?

Accepted Answer

**Target Audience:** Developers comfortable with routes and guards who need to decide how a routed screen gets its data — assumes [route guards](/interview-question/what-are-route-guards-in-angular) basics. **Difficulty:** Medium > **How to read this doc:** Plain language first, then 📌 Interview term: callouts. The timelines and results in sections 5 and 6 come from compiling the examples with ngc on Angular 22.2.3 and navigating with Router.navigateByUrl

Question 7

How do you handle SSR hydration mismatch errors using ngSkipHydration?

Accepted Answer

**Target Audience:** Developers who hit NG0500 hydration errors from a component they cannot easily rewrite. **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 example was AOT-compiled with ngc, rendered with renderApplication (Angular 22.2.3) and hydrated in jsdom, with and without ngSkipHydration; every

Question 8

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 9

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 10

What is the difference between computed() signals and standard method/getter calls in templates?

Accepted Answer

**Target Audience:** Developers who call methods in templates and want to know when it matters — assumes signals and basic change detection. **Difficulty:** Medium > **How to read this doc:** Plain language first, then 📌 Interview term: callouts. Every call count below was produced by compiling the examples with ngc on Angular 22.2.3, running them in jsdom and clicking through them; both examples also passed the playground mode, so you can run them here. ## 1. Why Th

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Easy

Explain the difference between FormGroup.patchValue() and FormGroup.setValue().

What are components and modules in Angular?

What is the purpose of ngOnChanges and how does it capture changes in @Input properties?

How do child components emit events to parents?

What are the types of data binding in Angular?

Medium

What is a route resolver and when is it useful?

How do you handle SSR hydration mismatch errors using ngSkipHydration?

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

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

What is the difference between computed() signals and standard method/getter calls in templates?

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

What is a directive and what are the types?

What do @HostListener and @HostBinding do?

Hard

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

How does compilation work under the hood in Ivy?

How does SSR hydration work in Angular — non-destructive hydration and mismatches?

What is NgRx?

Why use Renderer2 instead of direct DOM access?

How do you implement custom routing strategies by extending RouteReuseStrategy?

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

Explain how you can bridge Signals and RxJS observables using toSignal() and toObservable().