Guide on specifying the return type for Rx.Observable.fromPromise() in TypeScript

My current problem involves a function that returns an Rx.Observable created from a promise. Here is the code snippet:

var data$ = fetchData();
fetchData() {
    return Rx.Observable.fromPromise(fetch("someUrl"));
}

When I hover over the variable data$ in Visual Studio Code, it displays the type as Observable<Response>. However, if I explicitly declare the return type of the function like this:

fetchData(): Rx.Observable<Response> {...}
, I receive an error stating "Cannot find name 'Response'."

It does work when I declare the return type as Observable<any>, but that is too generic for my needs. How can I properly declare the function return type to match the Observable<Response> type of data$?

Answer №1

As the fetch-api remains in its experimental phase, users may not have access to all typings depending on their Typescript version. In such instances, one can consider installing the @types/whatwg-fetch typings via npm.

npm install @types/whatwg-fetch

To stay updated on any future developments, you can refer to this thread on github: https://github.com/Microsoft/TypeScript/issues/4948

Answer №2

Installing the types is a necessary step:

npm install --save @types/whatwg-fetch

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