How To Wait For Two Observables In Rxjs

Are you looking to level up your RxJS skills and wondering how to wait for two observables in your code? Well, you're in the right place! In this article, we'll walk you through a step-by-step guide on how to achieve just that.

When working with RxJS, you may often come across scenarios where you need to wait for multiple observables to emit values before proceeding with your logic. Thankfully, RxJS provides us with operators that make this task a breeze.

One of the most common ways to wait for two observables in RxJS is by using the `zip` operator. The `zip` operator combines the latest values from multiple observables and emits an array of these combined values whenever any of the combined observables emit a new value. This allows you to synchronize the emissions of multiple observables and perform actions based on their combined values.

Here's a simple example to demonstrate how you can use the `zip` operator to wait for two observables:

import { zip, of } from 'rxjs';

const observable1 = of('Hello');
const observable2 = of('RxJS');

zip(observable1, observable2).subscribe(([value1, value2]) => {
  console.log(`${value1} ${value2}!`);
});

In this example, we create two observables, `observable1` and `observable2`, each emitting a single value. We then use the `zip` operator to wait for both observables to emit values and log the combined values to the console.

If you need to perform a specific action only when both observables have emitted a value, the `forkJoin` operator can be your go-to choice. The `forkJoin` operator waits for all observables to complete and then emits a single value containing an array of the latest values from each observable.

Here's how you can use the `forkJoin` operator to wait for two observables:

import { forkJoin, of } from 'rxjs';

const observable1 = of('Hello');
const observable2 = of('RxJS');

forkJoin([observable1, observable2]).subscribe(([value1, value2]) => {
  console.log(`${value1} ${value2}!`);
});

In this example, we achieve the same result as with the `zip` operator, but with `forkJoin`, the subscriber will only receive the values once both observables have completed.

It's important to note that the `zip` and `forkJoin` operators have different behaviors regarding error handling. While `zip` will continue emitting values until all observables complete or one of them errors, `forkJoin` will propagate the error immediately if any of the observables errors out.

So, there you have it! By using the `zip` and `forkJoin` operators in RxJS, you can effectively wait for two observables in your code and handle their emissions synchronously. Try out these operators in your projects and level up your reactive programming game!