Rxjs Wait For All Observables In An Array To Complete Or Error

Have you ever found yourself working on a project that involves handling multiple asynchronous tasks with Observables in RxJS? If so, you may have come across situations where you need to wait for all the Observables in an array to either complete successfully or encounter an error before proceeding to the next step. In this article, we'll explore a handy technique to tackle this scenario efficiently using RxJS.

To wait for all Observables in an array to complete or error out in RxJS, we can leverage the power of combinators provided by RxJS. Specifically, we can make use of the `forkJoin` operator, which allows us to combine multiple Observables and wait for all of them to emit a value successfully or trigger an error.

Here's an example scenario to illustrate how you can apply `forkJoin` to handle a collection of Observables:

Typescript

import { forkJoin, of } from 'rxjs';
import { delay } from 'rxjs/operators';

const observablesArray = [
  of('Observable 1 processed').pipe(delay(2000)),
  of('Observable 2 processed').pipe(delay(1000)),
  of('Observable 3 processed').pipe(delay(3000)),
];

forkJoin(observablesArray).subscribe({
  next: (results) =&gt; {
    console.log('All Observables completed successfully:', results);
    // Proceed with the next steps here
  },
  error: (err) =&gt; {
    console.error('Error occurred:', err);
    // Handle the error scenario accordingly
  }
});

In this example, we have an array `observablesArray` containing three simulated Observables that each emit a value after a specific delay using the `delay` operator. We then use `forkJoin` to combine these Observables and await their completion. When all Observables have completed successfully, the `next` callback is triggered, providing an array of results containing the emitted values. If any Observable encounters an error during its processing, the `error` callback is invoked with the respective error.

By adopting this approach, you can effectively synchronize the completion of multiple Observables in an array and streamline your asynchronous workflows in RxJS. It enables you to coordinate and manage the flow of operations that depend on the successful resolution of parallel asynchronous tasks.

In conclusion, mastering the usage of `forkJoin` in RxJS empowers you to efficiently handle scenarios where you need to wait for all Observables in an array to complete or encounter errors before proceeding with subsequent operations. This technique enhances the robustness and clarity of your code, enabling you to build more reliable and responsive applications with RxJS.

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