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forkJoin() is an RxJS operator that waits for all provided observables to complete, and then emits the final combined result as an object.
values and users, which contain the last values emitted by their respective observable: 3 and an array of 10 users
forkJoin operators emits an object that contains the latest emitted value of each observable, in this scenario the number 3 and the array of users:forkJoin waits for all observables to be completed, we now add a delay to the HTTP call so that it takes 2 seconds before issuing the value.forkJoin emits only one value after 2 seconds because the of operator immediately emit the value while ajax.getJSON emits its values after 2 seconds and after completes.
As we said, forkJoin() waits for all provided observables to complete, and then emits the final combined result as an object.interval never completes and we stated the forkJoin emits the last value of each observable only when all of them complete.
Since the interval never completes, forkJoin never emits.forkJoin to emit a value, the interval should complete.
We can then use the take operator.
take(n) operator allows the observable to emit only the first n values it produces, after which it automatically completes. If the source observable emits more than n values, they will be ignored.interval operator creates an observable that emits 5 sequential numbers (0, 1, 2, 3, 4) every 1000 milliseconds (1 second) since the take(5) operator tells the observable to emit only the first 5 values.
After 5 emissions, the observable completes.forkJoin is used frequently in Angular when we need to perform multiple HTTP client operations and want to wait for the result of all operations to display the result or perform other operations.users and a list of posts from two different endpoints when a component is mounted.
At the end of the two fetches we can then display the data in the component template or perform other operations, with the certainty that both asynchronous operations have been performed successfully:
