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

To use the concatAll function from the RxJS library in JavaScript, you first need an observable that emits other observables. concatAll is used to flatten the observable into a single observable that emits all the values from the inner observables in sequence. Here's an example of how to use concatAll:

index.tsx
const { of } = require('rxjs');
const { concatAll } = require('rxjs/operators');

const outerObservable = of(of(1, 2), of(3, 4), of(5, 6));

outerObservable
  .pipe(concatAll())
  .subscribe((value) => console.log(value));
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In this example, outerObservable emits three inner observables: of(1, 2), of(3, 4), and of(5, 6). The concatAll function flattens these inner observables into a single observable that emits the values 1, 2, 3, 4, 5, and 6 in sequence. The subscribe method is used to subscribe to the flattened observable and log each emitted value to the console.

Note that concatAll is a higher-order function that takes an observable of observables, so you'll often see it used in combination with other RxJS operators like map and from.