README
until
Gracefully handle a Promise using async
/await
.
Why?
With the addition of async
/await
keywords in ECMAScript 2017 the handling of Promises became much easier. However, one must keep in mind that the await
keyword provides no standard error handling API. Consider this usage:
function getUser(id) {
const data = await fetchUser(id)
// Work with "data"...
}
In case fetchUser()
throws an error, the entire getUser()
function's scope will terminate. Because of this, it's recommended to implement error handling using try
/catch
block wrapping await
expressions:
function getUser(id)
let data = null
try {
data = await asyncAction()
} catch (error) {
console.error(error)
}
// Work with "data"...
}
While this is a semantically valid approach, constructing try
/catch
around each awaited operation may be tedious and get overlooked at times. Such error handling also introduces separate closures for execution and error scenarios of an asynchronous operation.
This library encapsulates the try
/catch
error handling in a utility function that does not create a separate closure and exposes a NodeJS-friendly API to work with errors and resolved data.
Getting started
Install
npm install @open-draft/until
# or
yarn add @open-draft/until
Usage
import { until } from '@open-draft/until'
async function(id) {
const { error, data } = await until(() => fetchUser(id))
if (error) {
return handleError(error)
}
return data
}
Usage with TypeScript
import { until } from '@open-draft/until'
interface User {
firstName: string
age: number
}
interface UserFetchError {
type: 'FORBIDDEN' | 'NOT_FOUND'
message?: string
}
async function(id: string) {
const { error, data } = await until<UserFetchError, User>(() => fetchUser(id))
if (error) {
handleError(error.type, error.message)
}
return data.firstName
}
Special thanks
- giuseppegurgone for the discussion about the original
until
API.