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

withLatestFrom is an operator on Observables provided by the rxjs library that allows you to combine the latest emissions from multiple Observables.

Here's an example of how to use withLatestFrom:

index.tsx
import { interval } from 'rxjs';
import { withLatestFrom } from 'rxjs/operators';

const sourceA$ = interval(1000);
const sourceB$ = interval(2000);

sourceA$.pipe(
  withLatestFrom(sourceB$),
).subscribe(([latestFromA, latestFromB]) => {
  console.log(`Latest from A: ${latestFromA}`);
  console.log(`Latest from B: ${latestFromB}`);
});
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In this example, we are creating two Observable streams using the interval function, which emits a value every X milliseconds. Then, we use withLatestFrom to combine the latest emissions from sourceA$ and sourceB$. The combined result will be an array with the latest emission of sourceA$ followed by the latest emission of sourceB$.

The subscribe function logs the latest emissions of each Observable stream. The console output will be something like this:

index.tsx
Latest from A: 0
Latest from B: 0
Latest from A: 1
Latest from B: 0
Latest from A: 2
Latest from B: 0
Latest from A: 3
Latest from B: 1
Latest from A: 4
Latest from B: 1
...
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This operator is very useful when you need to combine the latest emissions from multiple streams in an asynchronous way.