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

The takeLast() operator is used in RxJS to obtain the last n elements emitted by an Observable. It waits for the Observable to complete and then emits the last n elements.

Here is an example of how to use the takeLast() operator in JavaScript:

index.tsx
const { from } = require('rxjs');
const { takeLast } = require('rxjs/operators');

// create an observable that emits numbers from 1 to 5
const source$ = from([1, 2, 3, 4, 5]);

// get the last 3 elements emitted by the source observable
const result$ = source$.pipe(takeLast(3));

// subscribe to the result observable
result$.subscribe({
  next: value => console.log(value),
  error: err => console.error(err),
  complete: () => console.log('complete')
});

// Output:
// 3
// 4 
// 5
// complete
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In the above example, we import the from function to create an observable that emits values from an array. Then, we use the takeLast() operator to get the last 3 elements emitted by the observable. Finally, we subscribe to the result observable to log the emitted values to the console.

Note that takeLast() may not emit all items if the source Observable does not complete, so make sure to complete the Observable explicitly if necessary.