RxJS Observables: Emitting Values 1, 2, 3 in Multiple Ways

In RxJS (Reactive Extensions for JavaScript), you can emit values 1, 2, 3 using an Observable. Here's how:

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✅ Using Observable.create (Basic Example)

import { Observable } from 'rxjs';

const myObservable = new Observable(observer => {
  observer.next(1);
  observer.next(2);
  observer.next(3);
  observer.complete(); // Marks the observable as complete
});

// Subscribe to the observable
myObservable.subscribe({
  next: value => console.log(value),
  complete: () => console.log('Completed!')
});

// Output:
// 1
// 2
// 3
// Completed!

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✅ Using of() (Simpler Way)

import { of } from 'rxjs';

const myObservable = of(1, 2, 3);

myObservable.subscribe(value => console.log(value));

of() creates an observable that emits the given values synchronously.

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✅ Using from() (Convert Array to Observable)

import { from } from 'rxjs';

const myObservable = from([1, 2, 3]);

myObservable.subscribe(value => console.log(value));

from() converts an array into an observable that emits items one by one.

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✅ Using interval() to Emit 1,2,3 with Delay

import { interval, take } from 'rxjs';

const myObservable = interval(1000).pipe(take(3)); // Emit values every 1s, take 3 values

myObservable.subscribe(value => console.log(value + 1)); 
// Output: 1, 2, 3 (1 second apart)

interval() emits values at time intervals, and take(3) ensures it stops after emitting 3 values.

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Which One to Use?

• For synchronous emission → of(1,2,3)
• For array conversion → from([1,2,3])
• For delayed emission → interval(1000).pipe(take(3))
• For custom logic (async, API calls, etc.) → new Observable()