Your example can be simplified to:
from([1, 2, 3]).pipe( concatMap(id => fetch(`url-to-api/${id}`) .then(res => res.json()) ), ).subscribe()
Operators expecting an ObservableInput<T>, such as concatMap, automatically coerce promises to observables. And observables built from promises automatically complete when the promise resolves.
ObservableInput<T>
concatMap
From the rxjs source code:
export type ObservableInput<T> = SubscribableOrPromise<T> | ArrayLike<T> | Iterable<T>;
If you wanted to modify the promise's response, you can do that with an async function. For example:
from([1, 2, 3]).pipe( concatMap(async id => { const res = await fetch(`url-to-api/${id}`); const json = await res.json(); // do stuff return json; }), ).subscribe()
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Your example can be simplified to:
Operators expecting an
ObservableInput<T>, such asconcatMap, automatically coerce promises to observables. And observables built from promises automatically complete when the promise resolves.From the rxjs source code:
If you wanted to modify the promise's response, you can do that with an async function. For example: