promise-dedup

promise-dedup

Deduplicate any promise.

Cache promises by key

By default, dedup caches promises until they are settled:

import { dedup } from "promise-dedup";

async function doStuff() {
  await new Promise((resolve) => setTimeout(resolve, 5000)); // Waiting five seconds
  return 5;
}

dedup(doStuff, ["key", 42]);
dedup(doStuff, ["key", 42]);
dedup(doStuff, ["key", 42]);

// doStuff is only called once at this point

await new Promise((resolve) => setTimeout(resolve, 6000)); // Waiting six seconds

dedup(doStuff, ["key", 42]); // doStuff is called again because the previous promise settled

The third optional argument of dedup is the stale policy. By default, it's "settled". It can be set to "never" or to a number. When set to "never", the promise never gets stale. When set to a number, the promise gets stale after a timeout of that number as milliseconds.