RxJS Online Test

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About the test

The RxJS online test assesses knowledge of reactive programming concepts with RxJS and the various prebuilt operators that come with the library.

The assessment includes work-sample tasks such as:

  • Using RxJS Observables to manage asynchronously created data.
  • Working with RxJS Subjects for data broadcasting.
  • Processing streams of data with Pipeable Operators.

A good RxJS developer should be able to use reactive programming and the various prebuilt operators that come with the RxJS library to create maintainable and accessible web user interfaces.

Sample public questions

Easy
7 min
mca
Public
RxJS
Creation Operator
Pipeable Operator
RxJS Observable
RxJS Subject

Consider the following RxJS code for testing how a given damage Subject affects the health of a Player object in a game:

class Player {
  name: string;
  health: number;
  damageSubscription: Subscription;

  constructor(name, damageSubject) {
    this.name = name;
    this.health = 100;
    this.damageSubscription = damageSubject.subscribe((damage) => {
      this.health -= damage;
      console.log(this.name + " was hurt for " + damage + " damage");
    });
  }

  takeCover() {
    this.damageSubscription.unsubscribe();
    interval(1000)
      .pipe(
        takeWhile(() => this.health < 100),
        map(() => 10),
        tap(() => console.log(this.name + " is healing, current health is " + this.health))
      )
      .subscribe((heal) => {
        this.health += heal;
      });
  }
}
const explosion = new Subject();
const john = new Player("John", explosion);
const sam = new Player("Sam", explosion);

explosion.next(10);
john.takeCover();
explosion.next(20);

const paul = new Player("Paul", explosion);
sam.takeCover();
explosion.next(20);
paul.takeCover();

What options will be true after the above code is run?

Easy
3 min
mca
Public
RxJS
Creation Operator
Pipeable Operator
RxJS Observable

An online streaming platform uses the following RxJS code to log the number of seconds passed in a video:

const seconds = interval(1000).pipe(
  map((x) => x + 1),
  startWith(0)
);

const logger = seconds.subscribe((x) =>
  console.log(`Seconds passed: ${x}`)
);

setTimeout(() => {
  logger.unsubscribe();
}, 5000);

What options will be true about seconds and logger after the code above is executed?

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4 more premium RxJS questions

Awesome Tracking, Fresh Food, Log Post Data, Dictionary Definition.

Skills and topics tested

  • RxJS
  • Bug Fixing
  • Pipeable Operator
  • RxJS Observable
  • RxJS Subject
  • Creation Operator

For job roles

  • RxJS Developer

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