how to use the virtualtimescheduler function from the rxjs library in typescript

To use the VirtualTimeScheduler function from the rxjs library in TypeScript, you first need to import it from the library as shown below:

index.ts
import { VirtualTimeScheduler } from 'rxjs';
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After importing the VirtualTimeScheduler, you can create a new instance of it by passing a parameter which specifies the time unit used by the scheduler. For example, to create a new instance of the VirtualTimeScheduler using milliseconds as the time unit, you can do:

index.ts
const scheduler = new VirtualTimeScheduler(undefined, 0, 1);
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The first parameter (undefined in this case) specifies the now parameter, while the second and third parameters (0 and 1 respectively) specify the resolution of the scheduler in milliseconds.

Once you have created a new instance of the VirtualTimeScheduler, you can use it to simulate time-based events in your tests. For example, you can use it to create an observable that emits values after a specified amount of time:

index.ts
import { of } from 'rxjs';
import { delay } from 'rxjs/operators';

const observable$ = of('hello').pipe(delay(1000, scheduler));
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In the example above, we create a new observable that emits the string 'hello' after one second (1000 milliseconds) while using the VirtualTimeScheduler to control the timing of the emission.

Overall, the VirtualTimeScheduler function is a great tool for testing observables that produce time-based events.