piggybacker

Async keyed job runner, piggyback on results from running jobs with the same key

Usage

import { piggyback } from 'piggybacker'

async function fetchJSON (url) {
  const res = await window.fetch(url)
  return res.json()
}

const piggyFetchJSON = piggyback(
  fetchJSON,
  // Given the args that will be passed to fetchJSON, generate a key so that if
  // a second call is made while the first is in flight then the second will
  // ALSO receive the results of the first, instead of having to make a
  // separate request.
  function getKey (url) {
    return url
  }
)

const results = await Promise.all([
  // Multiple calls to piggyFetchJSON with the same URL _while_ a request is in
  // progress will not send another request! Instead they'll wait on the results
  // of the first.
  piggyFetchJSON('https://example.org/data.json'),
  piggyFetchJSON('https://example.org/data.json'),
  piggyFetchJSON('https://example.org/data.json')
])

// fetchJSON called only ONCE!

API

piggyback(fn, getKey)

Create a new function that'll call fn and piggyback on the results if called again.

• fn - the function to piggyback on
• getKey - a function called before each call to fn that generates a key for the call. Two or more calls with the same key will be piggybacked

Contribute

Feel free to dive in! Open an issue or submit PRs.

License

MIT © Alan Shaw