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

switchMap is an operator in the rxjs library for reactive programming in JavaScript. It is used to flatten higher order observables into a single observable.

Here's an example usage of switchMap:

import { fromEvent, interval } from 'rxjs';
import { switchMap } from 'rxjs/operators';

const button = document.getElementById('myButton');

// create an observable from button click events
const observableButton = fromEvent(button, 'click');

// use switchMap to switch to an observable of intervals every time the button is clicked
const subscription = observableButton.pipe(
  switchMap(() => interval(1000))
).subscribe(console.log);

// output: 0, 1, 2, 3, 4, 5, ...
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In this example, switchMap is used to switch to a new observable of intervals every time the button is clicked, and the resulting values are logged to the console.

Note that switchMap cancels any previous inner observables when a new outer observable emits, which can be useful for scenarios where you only want to handle the most recent events.