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I'm having a little trouble reading the rxjs documentation.
As far as I can see, this is the official documentation: https://rxjs-dev.firebaseapp.com/api
In the Observable documenation page under methods it has listed lift() and subscribe(), though later down the page, under examples, there are forEach(), pipe(), and toPromise().
None of those have usage notes - just argument specifiers.
Looking at this page: https://www.learnrxjs.io/operators/utility/topromise.html
We're told:
:warning: toPromise has been deprecated! (RxJS 5.5+)
How I am I meant to be reading this? toPromise was deprecated in 5.5x and continues to be deprecated?
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The toPromise function lives on the prototype of Observable and is a util method that is used to convert an Observable into a Promise . Inside this function we subscribe to the Observable and resolve the Promise with the last emitted value - attention - when the Observable completes!
As mentioned here, these are the main reasons why toPromise is being deprecated: One goal was to remove it from the Observable prototype and turn it into a standalone util function. The naming of toPromise is not the best. Especially when used in combination with await it does not read very well: await categories$.
RxJS allows to turn any Observable into a Promise with the firstValueFrom function (note: since RxJS 7, toPromise is deprecated): const obs = of(1); const promise = firstValueFrom(obs);
lastValueFromlinkConverts an observable to a promise by subscribing to the observable, waiting for it to complete, and resolving the returned promise with the last value from the observed stream.
TLDR; I think the documentation is incorrect.
toPromise is not deprecated.
Apparently there was some issue when toPromise was moved to operators and then removed in 5.5 beta.
toPromise was only available in rxjs/operators during a beta of 5.5. It was removed because it doesn't make any sense, it's not an operator, it's a method of subscription that results in a promise. See GH issue
Also there is no deprecation notice in the sources and none in the migration guide. Rxjs team is pretty reliable about deprecation warnings.
I think the documentation at https://www.learnrxjs.io/operators/utility/topromise.html is either wrong or it's referring to toPromise as operator - which has been removed.
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