Callforth

A tiny utility library to replace callbacks with Promises where possible.
Don’t callback, callforth!

It simply includes a hand-full of functions I see myself re-implementing in nearly every project.
So I might as well put them in a package.

Do things like:

await timeout(3000)

await eventOn(videoElement, "loadeddata")

const message = await eventOn(webWorker, "message")

Install

npm install callforth

Now you can:

import { eventOn, timeout, polling } from "callforth"

Alternatively, include this script and:

<script src="./path/to/callforth.umd.js"></script>
<script>
  const { eventOn, timeout, polling } = window.callforth
</script>

API

eventOn

const payload = await eventOn(target, successEvent, errorEvent)

Parameters

• target : EventTarget - any object you can call addEventListener on.
• successEvent : string - name of the event you want to await.
• errorEvent : string (optional) - if this event fires, the promise is rejected.

Return Value

• Promise<any> - wraps callback result (callbacks first argument)

timeout

await timeout(delay)

Parameters

• delay : int - milliseconds after which the Promise should resolves.

Return Value

• Promise<void>

polling

await polling(predicate, { maxTries, interval })

Parameters

• predicate : any -> boolean - delay in milliseconds after which the Promise should resolve.
• options : object (optional)
  • maxTries : int (default = 10) - maximum number of times to call predicate before giving up.
  • interval : int (default = 10) - delay in milliseconds between calls of predicate.

Return Value

• Promise<void>

More Examples

async function loadScript(url) {
  let script = document.createElement("script")
  script.src = url
  await eventOn(script, "loaded")
}

async function primesLessThen(number) {
  primeWorker.postMessage(number)
  const result = await eventOn(primeWorker, "message")
  return result
}