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

The concatMapTo() operator in rxjs library is used to flatten or merge the inner observables into a single observable sequence in a sequential fashion.

Here's an example of how to use concatMapTo() function:

index.tsx
import { interval, of } from 'rxjs';
import { concatMapTo } from 'rxjs/operators';

const source = interval(1000);
const example = source.pipe(concatMapTo(of('Hello World')));
example.subscribe(val => console.log(val));
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In this example, we first import the required functions from rxjs and rxjs/operators. We then create an observable sequence using interval() function which emits an increasing number every second.

Next, we create a new observable example using concatMapTo() function. of('Hello World') creates a new observable which emits the value "Hello World". The concatMapTo() function subscribes to the of('Hello World') observable for each emitted value from the interval() observable, thereby producing "Hello World" every second.

Finally, we subscribe to the example observable and log the emitted values.

This is just a basic example but concatMapTo() can be used in various scenarios to enable reactive programming in JavaScript.