This RxJS Online Test
Separates Good From Bad Hires

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?

Consider the following RxJS code for pushing and logging weather data:

const weatherSubject = new _______________({temperature: 0 , rainChance: 0});
const sendWeatherData = (weatherData) => {
  weatherSubject.____(weatherData);
};

sendWeatherData({temperature: 35.5 , rainChance: 20});
sendWeatherData({temperature: 34 , rainChance: 25});

weatherSubject.subscribe((x) => {
  console.log("Current Temperature: " +  x.temperature);
});

sendWeatherData({temperature: 28 , rainChance: 50});

weatherSubject.subscribe((x) => {
  console.log("Chance of rain: " + x.rainChance);
});

sendWeatherData({temperature: 25 , rainChance: 90});

Fill in the blanks above so that the following output is produced after running it:

Current Temperature: 34
Current Temperature: 28
Chance of rain: 50
Current Temperature: 25
Chance of rain: 90

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?