how to use the asyncsubject function from the rxjs library in typescript

AsyncSubject is one of the subjects provided by the RxJS library in TypeScript that resembles BehaviorSubject in many aspects. One of the primary differences between the two is that AsyncSubject only emits the final value emitted by the source Observable (or the default value if nothing was emitted) and then completes.

Here's a simple example of how to create and subscribe to an AsyncSubject using the RxJS library in TypeScript:

index.ts
import { AsyncSubject } from 'rxjs';

// Create a new AsyncSubject
const asyncSubject = new AsyncSubject<number>();

// Subscribe to the AsyncSubject
asyncSubject.subscribe({
  next: value => console.log(`Next: ${value}`),
  error: error => console.log(`Error: ${error}`),
  complete: () => console.log('Complete!')
});

// Emit a few values from the AsyncSubject
asyncSubject.next(1);
asyncSubject.next(2);

// Complete the AsyncSubject
asyncSubject.complete();

// Output
// Next: 2
// Complete!
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In this example, we first import the AsyncSubject class from the rxjs library. We then create a new instance of the AsyncSubject class and subscribe to it using an object that defines three callback functions: next, error, and complete.

We then emit two values using the next method and finally complete the subject using the complete method. The subscriber then receives only the last emitted value (2 in this case) and the complete function is called to indicate that the AsyncSubject has completed its operation.