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 callbag source instead of starting a new one. Once the source completes, the key is removed and the next call starts fresh.

Signature

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

Parameters

Parameter	Type	Description
fn	`(key: K) => V	Promise<V>`

Returns

A wrapped function with identical signature that coalesces concurrent calls, returning a callbag source.

Basic Usage

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

const load = keyedAsync((key: string) => fetch(`/api/${key}`).then(r => r.json()));
// Two concurrent calls for "user:42" → one fetch, two consumers
rawSubscribe(load("user:42"), (data) => console.log(data));
rawSubscribe(load("user:42"), (data) => console.log(data));