@jcoreio/once-async

async version of lodash.once that avoids retained promise memory leaks

The Problem

The following onceified function leaks memory:

1import once from 'lodash/once'
2export const getOnce = once(async () => ...)

The first call creates a Promise that is retained forever; and then/catch/finally handlers registered on this Promise will thus also be retained forever, as well as any objects in the closure of those handlers, causing the memory leak.

The Solution

All we need to do is discard the Promise once it's fulfilled, keeping only the resolved value or rejection reason for future function calls.

API

Example:

1import { onceAsync } from '@jcoreio/once-async'
2
3const fetchOnce = onceAsync(async () =>
4  fetch('https://com.com').then((res) => res.json())
5)

The created function calls your function once with the arguments and this binding of the first call to the created function. Subsequent calls will return a promise that resolves with the same value or rejects with the same reason as the promise returned by the created function.