keyedAsync()

Deduplicates concurrent async calls by key.

If a call for key k is already in flight, subsequent calls with the same key join the existing promise instead of starting a new one. Once the promise settles, the key is removed and the next call starts fresh.

Signature

function keyedAsync<K, V>(fn: (key: K) => Promise<V>): (key: K) => Promise<V>

Parameters

Parameter	Type	Description
fn	(key: K) => Promise<V>	Async function keyed by the first argument.

Returns

A wrapped function with identical signature that coalesces concurrent calls.

Basic Usage

import { keyedAsync } from 'callbag-recharge/utils';

const load = keyedAsync((key: string) => fetch(`/api/${key}`).then(r => r.json()));
// Two concurrent calls for "user:42" → one fetch, two consumers
const [a, b] = await Promise.all([load("user:42"), load("user:42")]);