Q: What is the difference between take(1) and first() operators in RxJS?

**Target Audience:** Angular developers who use take(1) and first() interchangeably to read "the current value" from a stream, and want to know when that difference bites. **Difficulty:** Easy to 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 5 was produced by running RxJS 7.8.2 (and the RxJS source q

Q: What is runInInjectionContext and when do you need to use it?

**Target Audience:** Developers who use inject() and the signal or RxJS interop APIs and have met NG0203 — explains dependency injection context from first principles. **Difficulty:** Medium > **How to read this doc:** Plain language first, then 📌 Interview term: callouts. Every error message and output below was produced on Angular 22.2.3: components compiled with ngc and run in jsdom, guards, resolvers and interceptors booted with a real appConfig

Question 1

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 2

What are route guards in Angular?

Accepted Answer

**Target Audience:** Developers who have routes working and now need to control who can go where — assumes basic routing knowledge. **Difficulty:** Medium > **How to read this doc:** Plain language first, then 📌 Interview term: callouts. The call order in section 5 is real output from compiling the example with ngc on Angular 22.2.3 and navigating with Router.navigateByUrl; it is not reconstructed from documentation. ## 1. Why This Even Matters — A Story

Question 3

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 4

What is the difference between take(1) and first() operators in RxJS?

Accepted Answer

**Target Audience:** Angular developers who use take(1) and first() interchangeably to read "the current value" from a stream, and want to know when that difference bites. **Difficulty:** Easy to 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 5 was produced by running RxJS 7.8.2 (and the RxJS source q

Question 5

How do you dynamically create components?

Accepted Answer

**Target Audience:** Developers building dashboards, modals, toasts, plugin systems or CMS-driven pages in Angular. **Difficulty:** Medium > **How to read this doc:** Plain language first, then 📌 Interview term: callouts. Both examples were AOT-compiled with ngc (strict templates) on Angular 22.2.3 and booted in jsdom, then clicked through; the first one also passed the playground's plain JIT mode, so it has a Run button. The quoted lines are the text of each element

Question 6

What is runInInjectionContext and when do you need to use it?

Accepted Answer

**Target Audience:** Developers who use inject() and the signal or RxJS interop APIs and have met NG0203 — explains dependency injection context from first principles. **Difficulty:** Medium > **How to read this doc:** Plain language first, then 📌 Interview term: callouts. Every error message and output below was produced on Angular 22.2.3: components compiled with ngc and run in jsdom, guards, resolvers and interceptors booted with a real appConfig

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