Basic usage

The _.defer functions lets you run an async function, registering functions as you go that should be deferred until the async function completes, and then executed. This is really useful in scripts where failure up to or after a specific point will require some cleanup. It’s a bit like a finally block.

A hat tip to Swift’s defer for the inspiration.

The function passed to _.defer is called with a single register function argument that can be used to register the work you want to be called when the function completes. If your function throws an error and then a registered cleanup function throws and error it is ignored by default. The register function supports an optional second options argument that lets you configure a rethrow strategy so that error in the cleanup function is rethrown.

import { defer } from 'radash'

await defer(async (cleanup) => {
  const buildDir = await createBuildDir()

  cleanup(() => fs.unlink(buildDir))

  await build()

await defer(async (register) => {
  const org = await
  register(async () =>, { rethrow: true })

  const user = await api.user.create()
  register(async () => api.users.delete(, { rethrow: true })

  await executeTest(org, user)


This _.defer function is 100% covered by tests. See them and contribute at GitHub.


See the source for _.defer on GitHub.