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

To use the firstValueFrom function from the rxjs library in TypeScript, you first need to import the firstValueFrom function from the rxjs package:

index.ts
import { firstValueFrom } from 'rxjs';
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Then, you can use it on any observable that returns a single value, like so:

index.ts
const observable$ = of('Hello World');

(async () => {
  const result = await firstValueFrom(observable$);
  console.log(result); // Output: 'Hello World'
})();
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The firstValueFrom function returns a promise that resolves with the first value emitted by the observable, and rejects if the observable errors or completes without emitting any values.

Note that firstValueFrom is an async function, so you need to use it inside an async function or with then() to access the return value. Also, make sure to handle the potential errors by surrounding the code with try-catch blocks or adding .catch() method after the function call.