@expo/results


An efficient, standards-compliant library for representing results of successful or failed operations. A result object represents the result of an operation that can either return a value successfully or fail. Typically we'd simply either return a value or throw an error, but sometimes we perform multiple operations as a batch, some of which may succeed and others fail. Since we can't simultaneously return values and throw errors, we instead return collections of result objects. This allows a batch operation to return values for successful operations and errors for failed ones without loss of information, namely the errors. (In contrast, sometimes it is appropriate for a batch operation to return just successful values and omit values for failed operations.)

Usage

Using Results

``ts
import { Result, result } from '@expo/results';

const results = await fetchWebPages(['https://expo.dev', 'http://example.com']);
for (const result of results) {
if (result.ok) {
console.log(result.value);
} else {
console.error(result.reason);
}
}
`

Creating Results

`ts
import { Result, result } from '@expo/results';

/**
* The purpose of this result API is to let you write functions that can
* partially succeed and partially fail and return all of that information to
* the caller.
*/
function fetchWebPages(urls: string[]): Promise[]> {
return Promise.all(urls.map(fetchWebPage));
}

function fetchWebPage(url: string): Promise> {
try {
const response = await fetch(url);
const text = await response.text();
return result(text);
} catch (e) {
return result(e);
}
}
``