how to use the mergeall function from the rxjs library in javascript

The mergeAll function is used in reactive programming to flatten nested observables into a single observable stream.

Here's an example code block using mergeAll:

index.tsx
import { of } from 'rxjs';
import { map, mergeAll } from 'rxjs/operators';

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

const obs2 = obs.pipe(
  map(val => of(val + 1)),
  mergeAll()
);

obs2.subscribe(console.log);
198 chars
12 lines

In this example, we first create an observable obs with values 1, 2, and 3. We then use the map operator to transform these values into observables that emit the original value plus one, resulting in three new observables. These three observables are then flattened into a single stream using mergeAll.

The output of this code block would be:

index.tsx
2
3
4
6 chars
4 lines

This demonstrates how we can use mergeAll to combine multiple streams into a single stream to simplify our code and make it easier to manage asynchronous events in our application.