NG Interview Set I - Observables Questions

Question 1

What are observables?

Answer 1

• They provide a declarative way of message passing between publishers and subscribers in an application
• They typically produce one or more values over time, which are subscribed to by observers
• They provide some advantages over promises

Question 2

What is RxJS?

Answer 2

• RxJS stands for Reactive Extensions for JavaScript, and is a reactive programming library centered around observables and operators making it easier to write complex asynchronous code

Question 3

How do observables differ from promises?

Answer 3

• Observables are declarative; promises execute immediately upon creation
• Observables can provide many values, whereas promises provide one value
• Observables are cancellable, whereas promiess aren’t
• Error handling also differs between them

Question 4

What are some advantages to using observables?

Answer 4

• Observables are cancellable; they come with powerful transformative functions (especially when using RxJS) to make asynchronous coding easier

Question 5

Does an observable compute anything if it has no calls to subscribe?

Answer 5

• No, it will not