pback

(piggy-back)

Any pure function in the form (...args) => Promise, can be passed to deduper and subsequent requests with the same arguments will wait for the result of the first one that arrived. This is meant to prevent unnecessary http or database requests.

npm install

/**
 * @param keyFn function that generates key for the internal cache, receives same params as the deduped function
 * @param fn function whose invocation is being deduplicated
 * @param options { timeout } - timeout in ms after which the task fails, default is 10s
 * @returns promise (same as the fn)
 */

  import { deduper } from 'pback';

  // an expensive async task that'll be repeated
  const getUser = (userId: number) => {
    return fetch(`/api/user/${userId.toString()}`)
  };

  const dedGetUser = deduper(id => id, getUser, {
    timeout: 1000,
  });


  // Consecutive requests will make only 2 fetches (as long as they arrive)
  getUser(1);
  // later
  getUser(2);
  // ...
  getUser(2);
  // ...
  getUser(1);
  // ...
  getUser(1);