RxJS Interview Questions and Answers
Freshers / Beginner level questions & answers
Ques 1. What is RxJS?
RxJS is a library for reactive programming using Observables, making it easier to compose asynchronous or callback-based code.
Example:
const observable = new Observable(observer => { observer.next('Hello'); });
Ques 2. Explain what Observables are in RxJS.
Observables are data streams that emit a sequence of values over time. They can be subscribed to, and observers can react to emitted values.
Example:
const observable = new Observable(observer => { observer.next('First'); observer.next('Second'); });
Ques 3. What is an Observer in RxJS?
An Observer is an interface that defines methods to handle the next, error, and complete events emitted by an Observable.
Example:
const observer = { next: value => console.log(value), error: err => console.error(err), complete: () => console.log('Completed') };
Ques 4. What is the purpose of the 'pluck' operator in RxJS?
'pluck' is used to extract a specified property from each emitted object in an Observable stream.
Example:
const pluckedObservable = sourceObservable.pipe(pluck('name'));
Ques 5. What is the purpose of the 'distinctUntilChanged' operator in RxJS?
'distinctUntilChanged' filters out consecutive duplicate values emitted by an Observable, only allowing distinct values to be emitted.
Example:
const distinctObservable = observable.pipe(distinctUntilChanged());
Ques 6. Explain the use of the 'interval' function in RxJS.
'interval' creates an Observable that emits sequential numbers at a specified interval, creating a timer-like behavior.
Example:
const intervalObservable = interval(1000);
Ques 7. What is the purpose of the 'take' operator in RxJS?
'take' is used to emit only the first n values emitted by an Observable and then complete.
Example:
const takenObservable = observable.pipe(take(3));
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