Angular Web Framework RxJS & Observables

Question 1

What is an Observable in Angular/RxJS?

Accepted Answer

A lazy collection of values that can emit multiple items over time and be subscribed to

Answer

A visual component for displaying data

Answer

A database query result set

Answer

A CSS animation sequence

Question 2

What is the difference between a Subject and an Observable?

Accepted Answer

A Subject is both an Observable and an Observer — it can emit values and be subscribed to

Answer

They are identical in every way

Answer

Subjects can only emit one value

Answer

Observables can push values while Subjects cannot

Question 3

What does the pipe() method do in RxJS?

Accepted Answer

Chains multiple operators together to transform, filter, or combine Observable streams

Answer

Sends data through a physical pipe system

Answer

Connects to a Unix pipe for command-line operations

Answer

Creates a new subscription to an Observable

Question 4

What is the switchMap operator used for?

Accepted Answer

To cancel the previous inner Observable and subscribe to a new one when the source emits

Answer

To switch between different programming languages

Answer

To map values from one data type to another

Answer

To toggle a boolean value in the stream

Question 5

Why is it important to unsubscribe from Observables?

Accepted Answer

To prevent memory leaks by cleaning up subscriptions that are no longer needed

Answer

Unsubscribing is never necessary in Angular

Answer

To improve the speed of the Observable

Answer

To reset the Observable to its initial value

Question 6

What is the async pipe in Angular templates?

Accepted Answer

A pipe that automatically subscribes to an Observable, displays the latest value, and unsubscribes on destroy

Answer

A pipe for asynchronous CSS rendering

Answer

A pipe for processing files uploaded asynchronously

Answer

A pipe for connecting to async database queries