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

You can use the timestamp() function from the RxJS library in JavaScript to get the timestamp (in milliseconds) for each item emitted by an Observable. Here's an example:

index.tsx
const { interval } = rxjs;
const { timestamp } = rxjs.operators;

const observable = interval(1000).pipe(
  timestamp()
);

observable.subscribe(value => {
  console.log(`Value: ${value.value} Timestamp: ${value.timestamp}`);
});
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In this example, we create an Observable that emits a value every second using the interval() function from RxJS. We then use the timestamp() operator to get the timestamp for each emitted value. Finally, we subscribe to the Observable and log the value and timestamp to the console.

Note that the timestamp() operator adds a timestamp property to each emitted value, which contains the timestamp in milliseconds since the Unix epoch (January 1, 1970, 00:00:00 UTC). You can then use this timestamp for various operations such as sorting or filtering the values emitted by the Observable.